I think you may need to use ShellExecute instead of AppBringUp.

Also: check the location of MeProc.exe. I found my copy in "c:\Program Files (x86)\" and not in "c:\Program Files\". The location might depend on whether you are using Windows 7, 10, or something else.

I just successfully tested this Dragon Advanced Scripting command to invoke a Macro Express script. I haven't tried it as a DVC script.

Sub Main
ShellExecute "C:\Program Files (x86)\Macro Express Pro 6\MeProc.exe /AGet title bar"
End Sub

The name of the Macro Express script is "Get title bar". There is no space after the "/A" switch.