You didn't read Jeff's post fully.

He said you could use a cell reference instead of saying ">2" and showed you how to do it with this example:

=SUMIFS(B1:B6,A1:A6,">"&D1,A1:A6,"<"&E1)
D1 (or whatever cell you choose) would hold the lower value
E1 (or whatever cell you choose) would hold the higher value