How can I tell the different between currency fields that ar

I'm having trouble with validation on currency fields. I'm trying to assess if the fields are null or not filled out for new records but it appears that the token for the currency fields are returning a zero (0) value despite never having been entered or touched. This is problematic because a zero value could be a valid response and I need to be able to tell the difference between a zero value currency field and a null value currency field. Is there another way I should be trying to perform the validation?