For Each r In Range("G" & lRowtoCopy).Resize(lHowManyCopies)
r.Value = InputBox("Enter value for " & r.Address, "Split Voucher Payments")
Next r
with this:
For Each r In Range("G" & lRowtoCopy).Resize(lHowManyCopies)
r.Value = Application.InputBox("Enter value for " & r.Address, "Split Voucher Payments", , , , , , 7)
Next r