Insert data into a form based on user input

[mmflynn]

You have a list menu field call company invoice number and 2 other fields
called customer name and cust invoice. Is there a way to have the user pick a
company invoice number from a input form and populate the customer name and
invoice on the same form without the user having to input the customer name and
invoice? Then once the form fields are filled in, I will click the submit
button and put the data in a table.