Post parked document and messages

Hi.

I have use a standard task TS00008142 for post parked document but I have a problem with messages.

Sometimes document that was parked not posted (reason balance for example).

There are 4 out ways on task:

a)Step executed

b)Processing obsolete

c)Parked document could not be posted & & & &

d)Parked document blocked & & &

But even that document not parked my task go every way nr 1.

How to trigger/support errors when document not posted?

Any advice?