Add multiple line items to new proposal

I am trying to add several new lines to a proposal. Basically, we want to be able to choose an item and automatically populate several items below that one depending on how many items a customer has currently purchased. Reading what I just wrote confuses even me, so let me be less abstract. We are starting to offer some hosted solutions for our current customers and on new proposals, we would like to be able to select a new item called (for now) Convert to Cloud. Upon setting that item I need to loop through all of the modules of