It works now, thanx everyone:
I now have "HL7.{PID:4.1} Contains "Relatie"" filled in the rule.
When testing i used the wrong Doctype apparantly, i should use: 2.4:ADT_A01
Probably the condition i posted in the beginning should have worked to, but this one is more simple to read and use.
When i do this, it works fine
HL7.RawContent CONTAINS "Relatie"
But there maybe other fields that can contain this word, so i want to narrow it down to the PID segment place 4.
This says that the first part was wrong initally: "HL7.{PID:AlternatePatientIDPID(1).ID}"
So how do i check on the PID segment, place 4?
Thanx, but the spelling is correct, i only translated the word into English, should'nt have done that.
On the other hand, now you know the Dutch word for Relation. 
I don't know the sollution you suggest (Objectscript), i will dive into this and see what i can learn.
Any tips on how to begin whit that?
Someone who knows what i am doing wrong in this Rule?