Referencing a Range
 

I have in the past referenced ranges using the following notation:
Set rng = worksheets().range(Cells(a,b),Cells(c,d)), rather than referencing
using the "A1" notation. Reason being is that I don't always know where the
range is going to begin or end. I could build a string to get to the "A1"
notation, but that doesn't have any appeal.

My current method of referencing a range is extremely flaky, are there any
other ways of doing this?