Mapping a string attribute from element A within a PI tag reference attribute in Template B

I have a template called "CHAMPION ARENA_North" and all of my PI tag attribute reference the PI Server name via an attribute called "PIHistorianSource". The PIHistorianSource attribute is being referenced from within the SAME template. Where PIHistorianSource = "PRODPISERVER1" (The name of the PI Historian)

 

My working element attribute relative path look like this

 

Element Attribute Relative Path: \\%@PIHistorianSource%\%..\..\ElementDescription%_%Element% - %Attribute%

Result: \\PRODPISERVER1\District12\HungerGames_Tornament - Attendees

 

We've decided to point this templates list of PI Tag attributes reference as well as many other templates containing PI tag attributes to reference "PIHistorianInput" from a different element called "SYSTEM" instead. This will allow us to change the PI Historian server from a single point of reference for testing purposes.

 

However, I am having challenges applying a functional remap to "PIHistorianInput" string attribute within the SYSTEM element. I have applied he following references with no success

 

\\%SYSTEM|@PIHistorianInput%\%..\..\ElementDescription%_%Element% - %Attribute%

\\%@SYSTEM|PIHistorianInput%\%..\..\ElementDescription%_%Element% - %Attribute%

\\%SYSTEM|PIHistorianInput%\%..\..\ElementDescription%_%Element% - %Attribute%

\\SYSTEM|PIHistorianInput%\%..\..\ElementDescription%_%Element% - %Attribute%

 

Any ideas as to how to map the element attribute relative path to achieve the same result?