Where to validate user input from FPM_FORM_UIBB?

I am supporting an ESS OVP app using WDA and FPM. 

This question concerns validating/changing user input from an edit page entered through FPM_FORM_UIBB

In a form, on an edit page, we wanted to mask the initially loaded value of a field with asterisks.

I used the feeder class get_data() method to accomplish this.

The user may then overtype the asterisks with content data.  At times, the user leaves some of the asterisks there as well.

I want to check the contents of the inpu field, and, if needed, compress out the asterisks.

if not inputfieldco '* ' .
translate inputfieldusing '* ' .
condense inputfieldNO-GAPS .
endif .
 

Where can I put this code? Or, where, generally, do you code validations of form data?

Thanks…  

…Mike