I find your post a bit confusing. The title refers to a function. You want a button to be able to select more than one item from this combo list because at present, you cannot (to be expected)? You aren't asking where to put the records based on multiple selections from a list - or are you??
I suspect you should have a listbox from which you can select multiple types, not a combo.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.