I am puzzled why each time when the same macro is running, there is a
different result, while after a few tims of running the macro, the result
stays the same thereafter.

There are two possible reasons I can think of:
1. The macro has a "Calculate" statement;
2. There is another workbook open.

I am not sure if any of the above two items is the reason of different
results by running the same macro multiple times.

Thank you anyone in advance who can give me some clue here!!

Laurie