GSP - getting supporting event Ids

When running GSP, I get all results as expected, however I would like also to get a list iof supporting events.

Let's assume that the data looks like: 

Cust 1, t1, event1, item1

Cust 1, t2, event 2, item2, item3

Cust 2, t1, event 3, item 1, item4, item 5

Cust 2, t3, event 4, item 2

...

In the  example above the event id is just a consecutive event number; every line of data has a different event id.  

So when I am getting a sequence as a result e.g.

<item 1> <item2> with its support value, I would like to output all the event ids that support this sequence.  In the example above these would be: (event1, event 2) and (event 3, event 4).  Alternatively this could be outputted : (cust 1, t1; cust 1, t2), (cust 2, t1, cust 2, t3)  - this would be the same info, just in a longer form.

Is there a way of doing this using the GSP operator or other RM operators?