VBA insert formula

Hello....

Bit of a basic question from what i understand, however im having major difficulty in doing this.

What i am trying to do is insert the following

=(A2 & " " & B2)

into D2 and the relevant code going down to D1000 so would result in

=(A1000 & " " & B1000)

, i thought this could be done using something like

Range("D2:D1000").Select
  ActiveCells.FormulaR1C1 = " = (RC[-3] &  "" ""  &  RC[-2])"

but not had any luck.

Any help you could give would be greatly appreciated.

Thank you in advance
Michael

Amazing thank you