I am trying to fill a listbox with data from a hidden Add-In Sheet.
I have tried a lot of things:

listbox1.RowSource = ThisWorkbook.Names("NWD").RefersToRange.Address(1, 1, ,
True)

and also

lbox_RowSource.RowSource = "=NonWorkingDays!A1:D100"

but it is only working, when I declare the property of ThisWorkbook IsAddIn
to false.

Is there a way to get around this limitation?
Thanks in advance,
Sven