Setting a Field Value based on defined Ranges

I need to set a field value in a table based on a set of aging buckets. For instance.

Set Aging Bucket to 1 if Days_Outstanding <=14

Set Aging Bucket to 2 if Days_Outstanding >14 and <=30,

Set Aging Bucket to 3 if Days_Outstanding >30 and <=60

Set Aging Bucket to 4 if Days_Outstanding >60 and <=90

Set Aging Bucket to 5 if Days_Outstanding > 90

Can someone help me with how to code this? I need to set it up as a workflow based on the value in the Days_Outstanding formula field.

I appreciate it.