Increase limit of itemListSpec for PopupMenu

Hi,

I try to list a huge (400+) number of values in a popupmenu (Frequencies) to choose from for further processing of data.
The string method:

PopupMenu popup0, value="99.968;102.86;105.85;108.92;112.04;115.33;"

does obviously not work because of "This method is limited to 1000 bytes of menu item text."
However also

PopupMenu FRQlistselector value=#getfrqs(w_frqs)

doesn't work either here. Is there another method to assign a big list of values or am I out of luck here?