My intention is to grab just the day from a field called "Contacts.Payment Start Date"

by using the following in a formula field on the same form:

Dayofmonth(${Contacts.Payment Start Date})

So for instance. If the payment start date is Dec.15,2012, I trying to get the value of 15.

However I'm doing something wrong I can't see as it's not working.

Any help appreciated.

Kerry