Triggering event with conditions?

[Kevin Yu]

I do not know if this is possible or not.  That's the reason I send this
message to see if anyone can tell me!
 
Here is the scenario, for example, I have three workflows all triggered
by Parked document created.  The three workflows all have different
tasks to perform based on document types.
 
Is it possible to put a condition against the triggering event such that
for certain document types only the corresponding workflow will be
triggered. Or, I have to build all these three workflows as
sub-workflows and called by a workflow which triggered by parked
document created.
 
Regards,