table and form design

[pjkbao]

I have the following tables/fields:

TABLE FIELDS
tblService ServiceID (pk)
ServiceType
CheckNumber

tblCheck CheckID (pk)
CheckNumber
InventoryBegins
InventoryEnds

tblInventoryUsed InventoryUsedID
InventoryUsed (pk)
ServiceID

I have a query (cartesian product) producing a combination of each check and
each inventory number associated with that check. Inventory numbers are
reused with various checks. I have a form where service is entered and an
unbound list box which pulls up the inventory numbers available based on
several things. I think that the selections that I make from the list box
should be saved into the table called tblInventoryUsed, but I cannot figure
out how to get the selections from the list box to save to that table. Also,
the ServiceID on the mainform should be populated into the ServiceID field in
tblInventoryUsed as to keep the service associated with the inventory numbers
used for that service. Several inventory numbers are used per service.
Any ideas would be so much appreciated.
PJK