[INUG-Users] db trigger issues

[Rolf Winterthur]

I have a field that is updated by a probe called Char3, I wish to take
Char3 and append it to Char2 when the event (same ident) happens
again, ie I wish for Char2 to relflect the history of Char3.
Event first happens, Char2 set to A        Char2 is then no longer
updated/set by probe.
second event happens Char3 is B and I wish to set Char2 = A - B and so on.
I've tried a db trigger pre db action reinsert

but it doesn't work.

What is the best way to do this ?

Thanks