Anyone can help me out?

I created a dialog and there are one edit box and two bottons in the dialog. User use editbox for browsing the file in the directories, and two bottons are used to identify the file user choose. tow bottons are called "top" and "bottom". Since I have two almost identical files(one is called "top" file and another one is called "bottom" file) in the directory, I have to make sure that user choose the right file. In those two files, there is a column called "TB", and under the column, there are only two types of data, "T" or "B". When user choose "Top" button, the related "top" file will throw away "B" type of data in the column, and only execute "T" type of data. In the same way, when user choose "bottom" button, the related "bottom" file will throw away "T" type of data in the column, and only execute "B" type of data. My questions are how to write the program for using those buttons (2)how to throw away those uncorrected data in the file according to user's choice ?
Thank you for your help.