.Row returns a Long.
Try:
<font face=Courier New><SPAN style="color:#00007F">Dim</SPAN> lLRow <SPAN style="color:#00007F">As</SPAN> <SPAN style="color:#00007F">Long</SPAN><br> <br> <SPAN style="color:#00007F">With</SPAN> ThisWorkbook.Worksheets("Sheet1")<br> lLRow = .Cells(.Rows.Count, "F").End(xlUp).Row + 1<br> End <SPAN style="color:#00007F">With</SPAN></FONT>