>I looked at delete trigger code and I cannot see there a check for child tableupdate(). However usually if parent is locked it is safe enough.

I couldn't find anything in any of the books or other sources I have, that's why I was asking. I ended up doing the following and it seems to work.

DELETE
IF !TABLEUPDATE() parent table then
  =TABLEREVERT()
  display msg saying so
ELSE
  IF !TABLEUPDATE() child table
    =TABLEREVERT()
    display msg saying so
  ELSE
    thisform.cmdnext.click()
  ENDIF
ENDIF

Which seems to work ok. It's still a big mystery to me. It's something I will play around with in the evenings... (That's the joy of having computers and programming as a hobby!)