how to change version # of exe file?

Is it possible to change the version number of exe file using NSIS that has already been created? I know I can get the version number using GetDLLVersion function, but can I change it? Thank you.

there may be api functions to do that, but i doubt it.

Do you know which API function?

You can compile your own little utility from the source code used in NSIS to change the version resource. You can also use Resource Hacker. With the correct command line parameters, it can be used to update resources silently.