Queries :: Truncate And Extract Value In String - Delimiter?

In Access 2007, in a table “Source” -> "UserName" column, I'm trying to truncate and extract value in the string:

a. Value within the parenthesis preceded by "".
b. Value outside the parenthesis preceded by “”

“Source” table contains the column ‘UserName’
“Final” table contains the columns ‘UserName’, “Expected_Output_1” and “Expected_Output_2”.

I tried using the following expressions to extract the output results, but unfortunately there’re not displaying the results in correct format.

For extracting results of “Expected_Output_1” I used: Mid([UserName],InStrRev([UserName],"")+1)

For extracting results of “Expected_Output_2” I used:

Mid(Mid([UserName],InStr([UserName],"(")+1,InStr([UserName],")")-InStr([UserName],"(")-1),InStrRev(Mid([UserName],InStr([UserName],"(")+1,InStr([UserName],")")-InStr([UserName],"(")-1),"")+1)

Attaching the database for your reference.

Expected results should match the snapshot attached or table “Final” in the attached DB

Example:
UserName = C103E000001 then the “Expected_Output_1” = E000001, “Expected_Output_2” = nothing

UserName = NAHoM\_INTRA_MTS (NAHoMDNAGAIntranetAdmin) then the “Expected_Output_1” = _INTRA_MTS, “Expected_Output_2” = DNAGAIntranetAdmin