Usualy, when you click "F5" it is to run a macro saved in your current workbook or other, depending on what environment you are...
The macro window SHOULD pop up..
If you want to execute a specific sub or User form you need to simply press the little "play button", while having your cursor in the specific sub or user form.
"Knowing that you know is the greatest sign of stupidity, knowing that you are ignorant is the best proof of intelligence.