Registry question

So I found that you can use the below command to extract registry keys.  I'm curious, is there a command that will allow you to extract only 1 string value or is that possible?

runwait(@comspec & " /c " & 'REGEDIT /E ' & '"%userprofile%\desktop\new\outlook profile.reg" "HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows Messaging Subsystem\Profiles\"', "" ,@SW_HIDE)

Lets say the key is HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows Messaging Subsystem\Profiles\test

There is a string value inside of that called called happy

What would be the command to extract only that 1 string value to a reg file instead of all of test?

Also lets say I want to run the outlook profile.reg file that got created using auto it.

What command would I use to run it especially while using variables like %userprofile%?