Pre-populate List Grid Data from External Source and save to populated form

I'm looking for a way to pull "template" data into a Grid Form that is a subform of another form and save it to the new form. 

I do not want to save changes to the table of "template" form.  I have a customer form (app_fd_account), an estimate form (app_fd_estimates) that can hold any number of descriptions of the itemized work to be done for the estimate. The estimate must have at least one description. I have stored the template data in a descriptions form (app_fd_desc_items).

So, (1) client record with an account#, tied to any number of estimates for that client, and any number of items in each estimate.

I have created some of the items in the template table that could be used in an estimate and created a List Grid to be used in the estimate. (I have it as a subform in the estimate form).  It pulls into the estimate file fine, but it does not save the selected data for the estimate.  I have also tried using the Multi Form Row in the List Grid of the estimate form it to get  it to save the data to the estimate. 

I am looking for options on how to make this work, I would like to pull in a list of the items in a pop up, have the user select one, populate a row in the List Grid of the estimate, and then save the description(s) to that estimate. Is another list form needed here?  Or is this not possible? 

Any help here would be much appreciated.