Excel Userform Rowsource replacement with compatibility for PC/MAC

I am trying to modify a workbook that works fine on PC to work on Mac, unfortunately it does use a rowsource call which does not work on mac. I have tried all the alternative solutions I have found here and on other sites and none of them work. Most will just return an Error 13 invalid property.

Here is the code I'm using that works for the pc to load the userform:

Private Sub UserForm_Initialize()
    LstEncounters.ColumnCount = 61
    LstEncounters.ColumnWidths = "70,55,14,55,14,55,14,55,14,55,14,55,14,55,14,55,14,55,14,55,14,55,14,55,14,55,14,55,14,55,14,55,14,55,14,55,14,55,14,55,14,55,14,55,14,55,14,55,14,55,14,55,14,55,14,55,14,55,14,55,14"
    LstEncounters.ColumnHeads = True
    LstEncounters.RowSource = "SavedEncounters"
End Sub

"SavedEncounters" is a workbook named range.

This should bring up a box that shows the cell information on a seperate worksheet that I can click on a row of data and hit load to populate another worksheet.

If I comment out the "LstEncounters.Rowsource" line the box shows but of course is empty. I have attached an example file, to launch the code causing the error on the "Encounter Builder" sheet click on View/Load button.

Any insight or ideas would be a great help. I have tried to use the list command but it is not working either.