I have two fields in my update form.

Field one is a hidden field with a value from the database.
Field two is a form field to change a value in a second database field.

I need to be able to validate that the second field number being entered is equal to or greater than the value in the hidden field.

I can't see any way to validate to a dynamic value or form field? I can validate to static values no problem, just not dynamic. Can this not be done?