Passing data between Forms

Here is my Problem,  I have a Form Called Main where user is required to enter a CustomerID, if he doesnt know the ID he can click on a search button which will open Search window for him to search. The result is then return as a grid where ge can then double click on to select the customer. I want to be able to send the selected info like customer ID and Name which i can get from grid back to the main form and populate the TxtCustomerID and txtCustomerName boxes.
To make matters worse, the user has the option to create a new customer. So in case the customer does not exist he clicks a new button which will open a new form to create a new customer. On save i also want to be able to populate the Main for text boxes.
Whats the best way to go about thet