I think you've nailed it - and I should have seen this - the range is not properly qualified; the Cells(…) parts need to be qualified:paying especial attention to the dots in the code. The With… End With consruct could probably span more than one line.Code:With Worksheets(WorksheetName)
VoltageDrop = WorksheetFunction.VLookup(Val(LoadCurrentText.Text), .Range(.Cells(10, Column), .Cells(26, VoltageDropColumn)), ReturnColumn)
End With

