Synchronizing / linking fields in a form

[signal hemlock]

I'm looking for a way to sync the values of two or more fields in a form.

Example; There are 3 fields copies, weight and totalWeight. I would like to make them synchronized such that editing the copies field should change the totalWeight and editing one of the weight fields should update the value of the other field.

[thorn heart]

are you planning on reusing those linked fields a lot, or just linking them up once?