Newbie: Need my combo box to populate another field based on selection (Part 2)

[Beeman]

First thanks for the response, and for the advice about spaces, I am going
to change them right now(I have spaces everywhere).

Here's what my relationships look like.
Company:CompanyName [1 --> Many] Account:CompanyName
Transaction:CompanyName [1 --> Many] Account:CompanyName
Transaction:AccountNumber [1 --> Many] Account:AccountNumber

here is the transaction table:
TransactionID
CompanyName
AccountNumber
AmountPaid
Date_Sent
Date_Widthdrawal
Comments
Date_Entered

What am/was hoping to do was to make a form using the Transaction table and
have CompanyName be filled in from a combo-box and when you select the
company name it populates the AccountNumber field in the transaction table
with the account number from the account table. This way I can enter the
company data from a seperate form and then add the account numbers from a
different form, and the working form will be the transaction form. *(is
there a way to make the transaction account field use a combo box just
incase I have a company that I have 2 or more accounts with ex. Verizon, 2
separate lines each with a unique account number * I might be pushing it
)