How can I get the process return value by NSIS script

Dear all,

I have an NSIS project ,and I use the following code line to uninstall my previous application

#R0 store the guid of my previous application
ExecWait '"msiexec.exe" /q /x $R0'

And I want to get the msiexec.exe return vaule to judge if my previous application can be uninstalled successfully,can any one know how to do it?

Thanks,
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Please read the manual before you ask.