Calling a form from an event handler using a filter

I added a button to a form to open another form but showing just some filtered records in the new opened form.

So I created the button, created an even handler using the "Run Form" event type. Since I want to open the AuditLog form showing records with EventType 20260 only, I added the following parameter:

AuditLog( FILTER(MessageType=20260) )

The AuditLog form opens but there is no filter set. When pressing the filter button on top of the form it's showing all records.

How can I get the form to show the filtered records only?

I tried the "Run Form as Linked Child" event type and using that filter condition as the link condition, but this didn't work either.