Filter list box based on combo box vb.net

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VB

Hello friends
I am Sarfaraz. I am developing a project in VB.Net and MYSQL. Friends my requirement is that if a customer comes and place an order for an item I am able to save the detais in the database but what if he order two or more items where can i save those details so that i can save all his details in the database and print a receipt.
I was trying to select an item from combo box and then filter list box based on that combo box and select multiple items from list box and then loop through all the items from list box to save details in table.

Secondly i have an invoice as auto increment field I want to add Account number of that customer so that whenever he comes again his details should be save in his account number. I was trying the account number as "XXX-invoice number ".
Please help

[PLEASE COMMENT IF YOU HAVE ANY BETTER IDEA ABOUT THE DESIGN OF THIS PROJECT. I AM NOT ABLE TO SHOW YOU THE DESIGN ON HERE BECAUSE I DO NOT FOUND ANY IMAGE LINK]

Thank you