Changing cell color using VBA

This would go to the last value in column Q:

Private Sub CommandButton1_Click()
dim n as long
dim data
data = range("Q2:R" & cells(rows.count, "Q").end(xlup).row).value
application.screenupating = false
for n = 1 to ubound(data)
If data(n, 2) > data(n, 1) Then Cells(n + 1, "A").Interior.ColorIndex = 3
next
End Sub