excal vba problem: range

Hi,
I have some coding as below, but i just don't know how to continue it:

......
dim rangeA as Range
dim sht as Worksheet
set sht=ActiveSheet
......
if aaa+1<>bbb then
       set rangeA = Range(sht.Cells(aaa+1,1), Cells(bbb-1,sht.UsedRange.Columns.Count))
end if

If <expression here!> Then
      msgbox "rangeA is valid"
      rangeA.select
      <more steps here....>
Else
     msgbox "rangeA is not valid"
End If

how i gonna write the code in the <expression here!> to determine whether the "rangeA" is a valid range or not. Meaning if aaa=2 and bbb=3, from the coding, we know that rangeA will be nothing. In the second "if-statement", i will check whether the rangeA is valid or not, if valid, i will do some manipulation on it, if not, i will continue to the next step. how to write it in code? hope somebody can help me on this a.s.s.p. I need it urgently. thanks!


cheers,
marry