Unfortunately there isn't an out of the box event that you could tap into that would trigger a script on a RITM or TASK when lines are added or removed from an MRVS to update another field on the catalog item.
I have done a few things where, as a value in a row is entered or changed you update a field on the form (using an onchange in the MRVS and some trickery, which you could instead employ as an onsubmit) and then, in theory, run the same script you have not, just onchange of a different field where you set the value onsubmit of the MRVS). That would only get you half-way there however.
I can't think of anything short of some very intrusive DOM manipulation that would let you take action and update an external field when a row is removed from a MRVS. It would probably require more effort to develop and maintain than benefit.
Maybe add a checkbox or something called recalculate to the form before or after the MRVS, hide it until you are on a catalog item or task, and then when the box is ticked (has a value of true) run your script to set the value, then at the end untick the box? It's not ideal, but sometimes you have to rely on Workflow Engine Mark I - human behavior - to get the job done.
I hope this helps!
If this was helpful, or correct, please be kind and mark the answer appropriately.
Michael Jones - Proud member of the GlideFast Consulting Team!
I hope this helps!
Michael D. Jones
Proud member of the GlideFast Consulting Team!
