specifying a range using a variable

[tryer]

This is just a simple question but I can't seem to find the answer in any of the hepl files. I want to refer to a range by using a variable but can't get the syntax right.
for example instead of

Range("AA3:AH3").Select
    Selection.AutoFill Destination:=Range("AA7:AH7"), Type:=xlFillDefault

which copies down the selected range I would like the row numbers be variables such as

Range("AA(rownum):AH(rownum)").Select
    Selection.AutoFill Destination:=Range("AA(final):AH(final)"), Type:=xlFillDefault

but what I have doesn't work