Excel property needed

How about something like this?

Sub defineRange()
    Dim rng As Range
    Dim Y As Integer
    Y = 12 'Or whatever you want it to be.
    Set rng = Range("A1").Resize(Y, 3)

    rng.Select 'You should delete this line - I put it in so 
               'you could see what's happening to your range.
End Sub

HTH