How to create a custom constant in a parameter section

For example, I would like to create a variable to store some directory in the [Files] section, like this: mydir=CustomDir; so I can reference it later when I'm importing my files

Source: "{mydir}\MyProg.exe"; DestDir: "{app}";
Source: "{mydir}\MyProg.chm"; DestDir: "{app}";

I want to do this 开发者_Python百科because later on I can easily change the directory of my importing files, and for other customizations in other parts.

Is there something in Inno that allow me to do that?

You can do this using the Inno Setup Preprocessor.

That is good for compile-time constants. If you wanted to set a variable at install-time, you could use Inno Setup's Pascal scripting.