'is within range'

Hi - hope someone can help. I'm trying to band records based on the value in a field. The field is $amountawarded_c in the opportunity module. I want to band the opportunities into 0-9999, 10000-24999, 25000-49999 etc. I've been playing around with 'iswithinrange' and 'ifelse' but have drawn a blank - anyone help???