Giving desired name to Wave Average wave output - can I modify a read only procedure?

override Function WaveAverageDoItButtonProc(ctrlName) : ButtonControl

override Function WaveAverageDoItButtonProc(ctrlName) : ButtonControl
    String ctrlName
    SVAR/Z ListExpression=root:Packages:WM_WavesAverage:ListExpression
    if (!SVAR_Exists(ListExpression))
        DoAlert 0, "Some data required for the operation cannot be found. Try closing the panel and re-opening it."
        return -1
    endif
    SVAR/Z ErrorWaveName=root:Packages:WM_WavesAverage:ErrorWaveName
    if (!SVAR_Exists(ErrorWaveName))
        DoAlert 0, "Some data required for the operation cannot be found. Try closing the panel and re-opening it."
        return -1
    endif
    SVAR/Z AveWaveName=root:Packages:WM_WavesAverage:AveWaveName
    if (!SVAR_Exists(AveWaveName))
        DoAlert 0, "Some data required for the operation cannot be found. Try closing the panel and re-opening it."
        return -1
    endif
    SVAR/Z WA_ListOfWaves=root:Packages:WM_WavesAverage:WA_ListOfWaves
    if (!SVAR_Exists(WA_ListOfWaves))
        DoAlert 0, "Some data required for the operation cannot be found. Try closing the panel and re-opening it."
        return -1
    endif
    NVAR/Z nSD=root:Packages:WM_WavesAverage:nSD
    if (!NVAR_Exists(nSD))
        DoAlert 0, "Some data required for the operation cannot be found. Try closing the panel and re-opening it."
        return -1
    endif
    NVAR/Z ConfInterval=root:Packages:WM_WavesAverage:ConfInterval
    if (!NVAR_Exists(ConfInterval))
        DoAlert 0, "Some data required for the operation cannot be found. Try closing the panel and re-opening it."
        return -1
    endif
    NVAR/Z ErrorMenuSelection=root:Packages:WM_WavesAverage:ErrorMenuSelection
    if (!NVAR_Exists(ErrorMenuSelection))
        DoAlert 0, "Some data required for the operation cannot be found. Try closing the panel and re-opening it."
        return -1
    endif
 
    String theList="", theXList=""
    String aWave
    String TopGraph=WinName(0,1)
    String TopTable=WinName(0,2)
    
    Variable DoConf
    Variable Interval
    Variable AppndGrph=0, numXWaves=0
    
    ControlInfo WaveSourceMenu
    Variable ListSource=V_value
    if (ListSource == 1)        // by Name
        theList = WaveList(ListExpression, ";", "")
    endif
    if (ListSource == 2)        // from Top Graph
        if (strlen(TopGraph) == 0)
            DoAlert 0, "There are no graphs"
            return -1
        endif
//      theList = WaveListfromGraph(ListExpression, ";", TopGraph)
        numXWaves= XYWaveListfromGraph(ListExpression, TopGraph,theList,theXList)
//      if( numXWaves == 0 )
//          theXList=""
//      endif
        ControlInfo AverageAppendToGraphCheck
        AppndGrph = V_value
    endif
    if (ListSource == 3)        // from Top Table
        if (strlen(TopTable) == 0)
            DoAlert 0, "There are no tables"
            return -1
        endif
        theList = WA_TableWaveList("*", ";", TopTable)
    endif
    
    Variable ErrorType = 0
    ControlInfo GenErrorCheck
    if (V_value)
        ErrorType = ErrorMenuSelection
        if (ErrorType == 1)
            Interval = nSD
        endif
        if (ErrorType == 2)
            Interval = ConfInterval
        endif
    endif
    
    Variable numWaves= ItemsInList(theList)
    if (numWaves == 0)
        DoAlert 0, "You have no waves selected. If you have selected From Top Graph, make sure the Wave Name Template is correct."
        return -1
    endif
 
    // Version 6.23: changed to Yes, No DoAlert
    if (numWaves == 1)
        // DoAlert 0, "You have only one wave selected ("+theList+" if you have selected From Top Graph, make sure the Wave Name Template is correct."
        //return -2
        String warning= "Only one wave selected ("+StringFromList(0,theList)+")."
        if (ListSource == 2)        // from Top Graph
            warning += " Make sure the Wave Name Template ( \""+ListExpression+"\" ) is correct."
        endif
        warning += "\r\rContinue anyway?"
        DoAlert 1, warning
        if( V_flag != 1 )   // 1 == yes
            return -2
        endif
        ErrorType=0
    endif
 
    Variable/G root:Packages:WM_WavesAverage:numWaves = numWaves        // for the New Graph button proc
 
    ControlInfo print
    if (V_value)
        Print "Averaging "+num2istr(numWaves)+" waves: "+ReplaceString(";",RemoveEnding(theList,";"),", ")
    endif
    Variable wasPointByPoint= fWaveAverage(theList, theXList, ErrorType, Interval, AveWaveName, ErrorWaveName)
    Variable disableXWave= 1    // hide
    
    if( wasPointByPoint >= 0 )  // < 0 means fWaveAverage reported an error
        if (AppndGrph)
            DoWindow/F $(WinName(0,1))
            aWave =  StringFromList(0, theList, ";")
            CheckDisplayed $AveWaveName
            if (V_flag == 0)
                String TInfo = traceinfo("", NameOfWave($(aWave)),0)
                String AFlags=StringByKey("AXISFLAGS",TInfo)
                String XWaveInfo = PossiblyQuoteName(StringByKey("XWAVE", TInfo))
                if (wasPointByPoint && strlen(XWAveInfo) > 0)
                    XWaveInfo = " vs "+StringByKey("XWAVEDF", TInfo)+XWaveInfo
                else
                    XWaveInfo= ""
                endif
                String AppCom = "AppendToGraph "+AFlags+" "+PossiblyQuoteName(AveWaveName)+XWaveInfo
                Execute AppCom
            endif
            if (ErrorType == 0)
                ErrorBars $AveWaveName, OFF
            else
                ErrorBars $AveWaveName, Y wave=($ErrorWaveName, $ErrorWaveName)
            endif
        endif
        if( wasPointByPoint )
            disableXWave= 0 // enabled and showing
        else
            disableXWave= 2 // disabled but showing
            // force calculated
            PopupMenu WavesAverageGraphXWave, win=WaveAveragePanel, mode=1 
        endif
    endif
    ModifyControl WavesAverageGraphXWave, win=WaveAveragePanel, disable= disableXWave 
    WA_ListOfWaves = theList
End