How to enable 'Multi Record Selection' in Custom form

Hi

I am developing a custom form to list all the open sales orders which are on 'Credit' hold. It is a tabular form listing the Sales orders.

The user can select a particular record and click on a button to release the hold on the corresponding order. we are good till this point.

The users need the capability to select multiple records (sales orders) and release the holds on all those orders together. SImilar functionality is available in 'Order Organizer - Summary' screen. we want this in the custom form. A little search lead me to use APP_MULTI.