Add Field in combo that populates price field

[John]

I am trying to create a sub form that allows me to enter the number of
products we have recived for an audit. My tables are:

tbl: Audit Data
Audit ID (PK) Links to (FK) Audit ID in Audit Items
Customer Name
Review Data
Reviews Name
Audit Status

tbl: Audit Items
ExID (PK)
QTY Found
Item Found
ProdID
AuditID (FK Linking to (PK) Audit ID in tbl: Audit Data)

tbl: Product Detail
ProdID (PK linking to (FK) ProdID in tbl:Audit Items)
Product Name
Product Price

1. I want to create a sub form that will display product name, Item Found,
QTY found and Product Price.

2. When I add data to this sub form, I want it to add the product aginst the
customer.

3. I need the product name field to be a combo box that allows me to choose
a product from a list, but then automatically populate the price field.

5. I need the Audit ID in tbl: Audit Data to automatically populate Audit
ID in tbl: Audit Items. I carnt seem to do this.

I have tried everything to produce this type of entry form, but seem to keep
failing. I have created query after query and also tried afterupdate but I
dont seem to be able to get it to work. I keep getting shouted at by my
girlfriend as I stay up all night trying to fix the issue. Help