I am new to macros and trying to make things as simple as possible, I have
this code which enters a formula into the cell to do a look up but the cell
then needs to be left unprotected but i get the error bit in the corner of
the cell. How could i do this in VBA code?

Thank you


Sub AutoFillSG()
ActiveCell.FormulaR1C1 = _

"=IF(RC[-2]="""","""",IF(R[-13]C[-2]=""WBM"",LOOKUP(R[11]C[-2],Densities!C[-5],Densities!C[-4]),LOOKUP(RC[-2],Densities!C[-1],Densities!C)))"
Range("H21").Select
Selection.AutoFill Destination:=Range("H21:H39"), Type:=xlFillDefault
Range("H21:H39").Select
Range("H21").Select
End Sub