Interraction between main programs and events

Hello everybody.

We want to develop a new global constraint with adjustment.

We use some events (suspend/4 and demon/1) on modification of domain
of variable and we call a C++ program which gives us if there is some
adjustments, no adjustement or no solution.

During the search (indomain),  we want that the main program fails if
there is no solution. At the moment, only the predicate calls by
events fails. But there is no repercussion on the main program.

Could you give us a solution to make interact the main program and the
predicate calls by the event ?

Best regards.