Hard to see in that tiny picture, but writing out the changed value in column 1 or column 2 or both is trivial. If one or more values change, you need to write a record. For each column, determine what to put in that column - a new value or a series of spaces. Then, write the record.
I modified my post. I wish i can create a logger like the one on the second picture. Can you suggest what can i do? thanks!!