Scripting Question - Renaming Files

Scripting Question.

I use MP3tag to organize and add tags to my TV shows. Some shows like Lost don't come with a year identifier while others like the reimagined Battlestar Galactica (2003) do. I want to standarize my files so every show contains the year identifier.

One solution I was using was to copy the grandparent directory to the album artist field then rewriting the filename using this structure

Z:\Television\\%albumartist%\Season $num(%discnumber%,2)\\%albumartist% - S$num(%discnumber%,2)E$num(%track%,2) - %title% $char(91)%year%$char(93)

Which works great unless you have an a double episode

Lost - S06E17-E18 - The End [2010-05-23].mp4

because of the "$num(%track%,2)" the episode number gets cut off.

So what is the easiest way to copy the name of the grandparent directory to the first string (series title) in each file? In other words...

Make --> Lost (2004)\Season 01\Lost - S06E17-E18 - The End [2010-05-23].mp4

Look like this --> Lost (2004)\Season 01\Lost (2004) - S06E17-E18 - The End [2010-05-23].mp4

Perhaps with the function Convert>Filename-Filename?
Source string: %1\%2\%3 - %4 - %5
Target string: %1\%2\%1 - %4 - %5

I read about variables in the help section but needed an example and this is perfect. Thanks.