Copy selected records from PopUp-Form to subForm1 on MainForm

[SockMonkey]

Here is a brainstumper.

I don't want the easy way out of choosing records from a combo box.

Currently I have a MainForm with Tenant and Selected Property he the tenant is interested in.
SubForm1 is where we will place data on the PropertySpaces the Tenant is interested in.
I have a button on SubForm1 which opens PopUp-Form showing the PropertySpaces for the specific property.This part works fine.

The Problem: I am stumped on a way to select multiple records from the PopUp-Form and once I go to close the PopUp-Form have the data from each of the selected records
copy into SubForm1.(can't use multi-select list box as may need to make a changes to records in PopUp-Form)
The fields in SubForm1 are the same as those in PopUp-Form.
The key field in PopUp-Form is [PropSpaceID]

All help is appreciated.
Thank You.