"Append" a value to MS_DGNLIBLIST Config Variable path?

I wish to "append" (>) another library path to the MS_DGNLIBLIST variable within my MVBA.

1.
I can use the following but it replaces the value. How can I append a value please?
' Reset value of configuration variable path
ActiveWorkspace.AddConfigurationVariable "MS_DGNLIBLIST", "C:/Documents and Settings/All Users/Application Data/Bentley/Microstation/08.11.07.443/EE_WORKSPACE/WS_Standards/Standards/dgnlib/PrintStyles/ZS_PrintStyles_PORT_LEGACY_GREY.dgnlib"

2.
I also wish to use a variable for part of the path name than hardcode it?
' Append a value to the configuration variable path
ActiveWorkspace.AddConfigurationVariable "MS_DGNLIBLIST" > "$(_EE_STANDARDS)DGNLIB/PrintStyles/ZS_PrintStyles_PORT_LEGACY_GREY.dgnlib"
' Workspace Variables used
' _EE_STANDARDS = C:/Documents and Settings/All Users/Application Data/Bentley/Microstation/08.11.07.443/EE_WORKSPACE/WS_Standards/Standards/

Cheers, Colin