Hi Randy, thanks for solution. I've bought the plugins (unfortunatelly documentation is really poor, I have to study PHP now :) )
Regarding computation rules, I found out that if let say add a rule to summarize two values from input field,...it doesn't work as expected.
Unfortunatelly, computation is done "on change", so if you let say create two fileds A & B, and if you will apply A+B rule on B field,...and will change A several times,...the B will be summarized exactly the same times. "on keyup" the same story.
Seems that something is missing in js.
I've added request in tracker because I don't have experience to change the functionality
http://www.seblod.com/resources/tracker/11522?thanks=seb_tracker_comment