VS 2012 Loop then insert into rich text

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Okay. So this is my application so far. the user inputs coupon information (on the main screen) and it prints out a formatted template a retail system could read (bottom screen). After the first 3 rows are formatted on the main form (PLU output, 3 rows), the user then had to add exclusions. Exclusions would be like a department or some item that is excluded from the coupon.

I need to figure out a way to receive user input (type, identifier, department) thats on the second form and add them underneath the information in the richtextbox on the main screen.

I know how to format it correctly, I just want some advice on the best way to collect and store information, and then how to place it under the PLU output on the main screen.

should I do a popup box on the main screen that when the user clicks 'exclusions' a pop up box asks for how many and then records separate information for each exclusion?

or should I collect information on the second form and then transfer it to the rich textbox in form 1?

And how could I receive the input and continue below the template the main form has created without clearing the information from form1 and replacing it with the coupon exclusions?

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