Get partial string before character

Get partial string before character

Hey everyone,

I've been trying all sorts of things based on my knowledge in excel formulas, but impossible to get it done because the functions I normally use do not exist in Zoho :( 

I need to grasp the left part of a string column, after the first character '-' from the right :
ex : "PR - SOLID STATE LIGHTING SOURCES - OVERVIEW"
I need to grasp  "PR - SOLID STATE LIGHTING SOURCES"

Any ideas ?