execute macro from personal.xlsb and get the value of the variable

Unless you have messed up your version of excel

The personal workbook is open when excel is open. It is opened as hidden.

The Macro in the personal workbook will not do what you expect.

I think it should be:-

Public Function get_boards(Col As Integer) As Integer

get_boards = Cells(Rows.Count, 1).End(xlUp).Row

End Sub

Once you have edited the macro

type =get_boards(1) in any cell

It will return the last row number in column A.

type =get_boards(2) in any cell

It will return the last row number in column B.