I did it the other way round, but it’s essentially the same:
![0EM50000000Sj7Z.jpg 0EM50000000Sj7Z.jpg](/t5/image/serverpage/image-id/13274iBB53E4C2CB5129AA/image-size/large?v=v2&px=999)
So is there really no way to react on a data value change via a web form directly?
I still wonder what the “Source” constraint is for, since I haven’t seen any value suggestions for this constraint by now: