You will need to be creative.
You could use an ActiveX control maybe or another browser window to make the selections and then pull them into your form.
Otherwise work something similar with another control like check boxes or drop down lists.
If you used a backend table you could have your dataitems and then another selection field. Then you could display the table and have checkboxes which toggled the selection field and then use the records which were selected.
You may want to check out the Database Accelerator if you choose to go the table route. Qdabra Database Accelerator Suite Version 2.1 - Developer