Can not Extract File during Installation

[InstallationWay]

I have faced a problem with inno setup and you, friends may know something helping me.

I have a custom shaped setup, also I have a custom exit message which using some images.

- before installation, if you press the `X` button you will not get any error and everything works great.

- Press install, the installation will start. now try to cancel the process. The exit message box should display. But It gives an error that the setup can not find a specific image to extract.

- Just try to put a big file size (for example about 30 MB) for installation. I have commented it as BigSizeFile in the [Files] section.

How to avoid such a treat? is there any trick? it seems the inno setup can not install a file and parallelly extract a file into the temp.

Thanks

 

[InstallationWay]

Thanks to Cesar82,
Answer is:

It is a native error of Inno Setup that does not allow extracting files while installing.
You cannot create buttons on the same variable more than once in a variable longint.
Just change it to create the form exit in initializewizard.