C++: How to programmatically create a local user logon credential in Windows Credential Manager so “runas /savecred” can use it?

I am trying to set an executable to run as a local low-privileged user (different from the current logged-on user) by default. The Windows command "runas /savecred /user:username appname.exe" can do it, but it requires the current logged-on user to manually type in password of the different user at the first time. Ideally, I want the installer of the program set the credential, so no interaction would be needed for the current logged-on user. (I don't want to make the program as a Windows Service for other good reasons.)I am trying to set an executable to run as a lo