prepopulate one form with data that has been previously entered in another form

prepopulate one form with data that has been previously entered in another form

I have two forms - one COMPANY (contains names and addresses of companies I deal with) and another PARTS (all parts I stock, can have multiple parts from one company). I have on the PARTS form a lookup for a COMPANY NAME from the COMPANY form. Now as I select the COMPANY NAME from the list I would like to have fields for the address, city, state, zip from COMPANY form update on the PARTS form. I saw the example here http://help.creator.zoho.com/Fetch-and-Update-Records.html but cannot implement the "How can I prepopulate one form with data that has been previously entered in another form, in same application?"