Need Assistance with some xml/xsl code and future projects if all goes well

I have some xsl code that is used in a custom software program I will periodically need to update. I need someone to assist me in this until I get familiar and comfortable with it. A lot of these are taking templates for software and restricting what is shown on it. The current simple project is a template that is used for an airline program. It displays the airline, what terminal its coming from, the gate, and the level. This data comes automatically from a database. Sometimes what happens is the data from two different flights comes in, and it displays the same exact information (aka two different flights from the same airline on the same terminal and have the same bag gate). I need to make some sort of statement that compares what is pulled and if it is the same data as an existing flight, then it does not appear on the screen, hence avoiding duplicates.