Macro to rename workbook

This saves the active workbook as the values in the three cells you specified. Put it in a module.

Public Sub saveas1()

ActiveWorkbook.saveas Filename:=Cells(2, 1).Value & Cells(3, 1).Value & Cells(1, 2).Value

End Sub

It should work, but I'm uncertain because you say the extension currently used is .wk1.