Hello everybody and thank you for reading,

I'm working on a little project where I have a content type made of two field (the title and and a text, numeric, field), I'm trying to do create a form that from frontend is able to modify one of this field by subtracting the specified amount.

For example:
Title: Zend
Points: 300
input field: 50

that should result in
Title: Zend
Points:250

Now, to have something like that I thought I had to use a custom form template but I immediately realized that something was wrong, I started from the seb_minima template and editing mainbody.php I called my value as echo $cck->get('art_title')->value; or echo $cck->get('art_title')->form; , according to my needs but when submitting my value I had everything "resetted", the title was changed to the date, the other value just empty.

Could someone tell me if Is there a way to do the operation without modifying the template? Maybe using some javascript in the field?
Is there some kind of reference to see how a custom form template is done, anyway?

I'd need some directions, please :)

Have a nice day!

R.