Setting a cell in another workbook

When I try to set a cell in another workbook I get the error Application-defined or object-defined error. Any ideas?

   Do Until IsEmpty(Workbooks("" & mybook & "").Sheets("QUOTE").Range("A" & lngMyRow))
     
Set FSetup = Workbooks("" & mybook & "").Sheets("QUOTE").Range("MinutesSetup").Cells(lngMyRow, 1)

   If FSetup = "" Then GoTo LEND
        
   If FSetup.HasFormula Then
        GoTo LEND
   Else
   Workbooks("" & mybook & "").Sheets("QUOTE").Range("AD").Cells(lngMyRow, 1).copy
   Workbooks("" & anotherbook & "").Sheets("QUOTE").Range("MinutesSetup").Cells(lngMyRow, 1).PasteSpecial (xlPasteValues)
   End If
           
LEND:
        
    lngMyRow = lngMyRow + 1
 Loop