you can also use "if" statement as in your expression :
sum(if(FGH = 'CMO',MV)).
and if you want in dimension, then click on add calculated dimension and write : = if(FGH = 'CMO',FGH)
By using this dimension in straight table it only shows CMO as mention below. when you use in dimension then your expression will be sum(MV).
XYZ FGH MV ABCDE CMO 100.00 LMNO CMO
Hope it will help you