How do I pass data from one form to another form?

How do I pass data from one form to another form?

Hello,

I'm trying to build a personal financial planning database.  I want to pass the "Transaction Amount" from a Transaction Entry form to a similar field in a Transaction Summary form. 

The link between the two forms is the Transaction ID ("ID" in the Transaction Entry form and "Transaction ID" in the Transaction Summary form).

I have been able to create a link between the two forms and pass the ID, but I'm confused about how to pass the Transaction Amount. 

Thanks so much,

Ann