minus and divide in if condition

[capriconuser]

hi 

i have   a data like this 

Mail BOX  Total Size

34.25 GB    50 GB

12.35 MB   50 GB

I want like if there is GB in Mail Box column data then want to minus that to 50 GB and if there is 'MB' then want to divide /1024 

for example

34.25 - 50

12.35 /1024

how i do this through if condition in set expression?

help plz

[MayilVahanan]

HI @capriconuser 

Try like below

If(Right([Mail BOX],2) = 'MB', KeepChar([Mail BOX], '01234567890.')/1024,
KeepChar([Mail BOX], '01234567890.') - KeepChar([Total Size], '01234567890.'))