VS 2005 master and details saving

hi all ,
well , i have invoice form separated into 2 parts the upper part is master (header) and detail (body) in invoices where header contains date,name,invoice number,etc ..and the lower part is the body contains the datagridview with its details like the item name or code,qty,price,discount,etc ..
the problem is i want to save the invoice headers in a table and the body in another different table but with a realtion between the 2 of them by the invoice id i think i put it in the invoices' form load. but i cant get it right .
so if any one have an example by code 2 solve this prob , please send .
by the way iam using vb. net 2005 and my db is sql 2005.
thanx all .