Hi Stefan
I can think of two possibilities.
The first would be to use a HOTSPOT
It uses the value of an attribute to specify a special location in a graphrep where a link (following a reference/INTERREF or a programcall) should be. So you could create a HOTSPOT over the list of INTERREFS, however I have no idea how a HOTSPOT behaves if there is more than one reference.
An alternative could be to use CLIP_RECT, which specifies a region where only inside of it elements are drawn and not drawing anything outside of it. So after setting the CLIP_RECT you should be able to simply output the INTERREF attributes using ATTR. However you would have to know how big it needs to be to show exactly x INTERREFS, but you should be able to determine this using your current list of x elements and TEXTBOX to determine its size.
I hope this helps you more than it confuses anybody

Best regards,
Patrik