WoodrowA,
If I were you I would use what you called:
"a modal or popup window with the data (for one record of the grid) is in form view"
This is typically referred to as a linked form.
Fortunately there is a button wizard that will write all the code for you.
Create a Form in Single form view, that is based in the Subform's RecordSource.
Then, on your main form, drop in a button.
When the wizard opens, select: Form Operations-->Open form
Select your newly created form
Select: "Open the Form and find *Specific* data to display"
Click the common field from both forms, and click the <-> button
Select either text or a picture
Name your button
Now when you are on the main form and you click the button, the second form will open displaying only those "child" records associated with the "Parent" form.
JeffCoachman