searching for and adding data to existing row

hi, i am pretty new to vba and can create basic user entry forms but i cant work this one out

A, B, C , D, E, F, G
batch number, product name, product type, bar-code, date sold, sale price, postage costs

I have a user-form to enter columns A - D these are my "inventory columns" and columns E - G are for when i get a sale.
is what i need is when i get a sale, is to be able to scan the bacode in to the "sales" user form to search for the record, and add the relevant sale data to the record on the same form as where i scanned the bar code

i have a completed user form to enter columns A-D but not yet for E-G

i have a few applications where a soloution to this problem would help, your help would be appreiciated and thanks in advance