Link two subforms in datasheet view (one sub-form, one sub-subform

I’d like to know if this is even possible. I have a form named “Frm
Volunteer Opportunities� with a subform named “SubFrm Volunteer
Opportunities�. The subform must remain in datasheet view and has fields
like: [Event ID], [Event Date], [Start Time], [End Time], etc... I want to
link another form (a sub-subform?) to the datasheet so that whenever my
curser is located in one of the datasheet rows, this other form will present
all volunteers scheduled for that event. Then, when you move the curser to
the next row, those names would change. I’m guessing this means that the
mystery form will also need to remain in datasheet view. This third form
will have fields like [Event ID], [Volunteer ID], [First Name], [Last Name],
etc... Clicking the + sign on each row to view this data isn’t my ideal
preference.

Any advice, hints, or nudges to get me started would be greatly appreciated!