User interface to select multiple files and folders

function myIO_Panel()
    // make global text wave to store paths and output folder
    if (!WaveExists(root:Packages:myFolder:Path))
        NewDataFolder/O root:Packages
        NewDataFolder/O root:Packages:myFolder
        Make/T/O/N=3 root:Packages:myFolder:Path
        wave/T Path = root:Packages:myFolder:Path
    endif

    NewPanel /W=(81,73,774,248)
    Button SelectFile1,pos={12.00,10.00},size={140.00,20.00},proc=ButtonProc,title="Select File No. 1"
    Button SelectFile2,pos={12.00,41.00},size={140.00,20.00},proc=ButtonProc,title="Select File No. 2"
    Button Output,pos={13.00,72.00},size={140.00,20.00},proc=ButtonProc,title="Select Output Folder"
    SetVariable File1,pos={168.00,13.00},size={500.00,14.00},value= Path[0]
    SetVariable File2,pos={168.00,43.00},size={500.00,14.00},value= Path[1]
    SetVariable File5,pos={168.00,75.00},size={500.00,14.00},value= Path[2]
    Button DoIt,pos={291.00,121.00},size={100.00,20.00},proc=ButtonProc,title="Do It"
end

// define buttons
Function ButtonProc(ctrlName) : ButtonControl
    String ctrlName
   
        wave/T Path = root:Packages:myFolder:Path
        variable refnum
   
        strswitch(ctrlName)
       
            case "SelectFile1"  :
                // get File Paths
                Open/D/R/F="*.tif"/M="Select fist file" refNum
                if (strlen(S_FileName) == 0) // user cancelled or some error occured
                    return -1
                endif
                Path[0] = S_fileName
                break
       
            case "SelectFile2"  :
                // get File Paths
                Open/D/R/F="*.tif"/M="Select fist file" refNum
                if (strlen(S_FileName) == 0)
                    return -1
                endif
                Path[1] = S_fileName
                break
       
            case "Output"   :
                // set outputfolder
                NewPath/Q/O OutputPath
                PathInfo OutputPath
                Path[2] = S_Path
                break
           
            case "DoIt" :
                // run your loadwave commands and other functions
                DoStuff(path)
                break
       
        EndSwitch
End

// run your stuff
function DoStuff(path)
    wave/T path
   
    print "LoadWave from: " + Path[0]
    print "LoadWave from: " + Path[1]
    print "Calculate output and save to: " + Path[2]
end