Why Click Abort Button not work

Hi,
I use File Command ,It Shows a MessageBox with Abort ,Retry,Cancel Buttons,When the file is occupied.The user click Abort Button ,it is not working to exit install program?
Thank you very much for hlep

I want to know that how to handle it when the user click the "Abort" Button.For Example,The user clicks the "Abort" Button,The install programe exit.

Is this your NSIS code?

A normal installer will "Abort" when you click abort in that dialog and no further Sections will be executed.