VBA to copy formulas in column D and paste as values in same column

I have create a formula in column D. Once the formula is created, I want to copy and paste as values. I am try to make the code more efficient by not having select the cells in the process. I've tried both methods below, but can't get either to work. Thanks

Range("D2:D" & Lastrow).FormulaR1C1 = "=IF(LEFT(RC[8],3)=""TEN"",""RR-12"","""")"
Range("D2:D" & Lastrow) = Range("D2:2" & Lastrow).Value

Range("D2:D" & Lastrow).FormulaR1C1 = "=IF(LEFT(RC[8],3)=""TEN"",""RR-12"","""")"
Columns("D:D").copy Destination:=Columns("D:D")Paste:=xlPasteValues

Hello, have you supplied us with the complete code you are using?

For example

Dim LastRow As Long, Rng As Range
LastRow = Cells(Rows.Count, "A").End(xlUp).Row
Set Rng = Range("D2:D" & LastRow)
Rng = "=IF(LEFT(RC[8],3)=""TEN"",""RR-12"","""")"
Rng = Rng.Value

Alternative method:

Sub snb()
  Sheet1.Cells(1).CurrentRegion.Columns(1).Name = "snb2a"
  [snb2a].Offset(, 3) = [if(left(offset(snb2a,,7),3)="TEN","RR-12","")]
End Sub