Custom subject on Incident template based on Requester information

Custom subject on Incident template based on Requester information

Servicedesk Plus MSP 9.2 Build 9208

So I'm trying to figure out a Field & Form Rule for my template that makes it fill in the Subject automatically when the Requester field is changed.

So if the Requester is in Department X the subject would change to

"X Pinpad incident"

But I can't select Requester as a "OnChange" item in Field and form rules.

Also it's important that the technician can change the subject after that has been done.
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