I am using the properties tab builder to input information for a part into the properties in the summary information.  I have created a list box that lists a room number where the part will be found along side a description relating to that room  i.e. "100 - plant room".   I included the description to make it easier for the user to pick the right number, but don't really want the description to appear in the summary information (only the room number). 

Is there an expression / formula I can use to define another property in the summary information that will allow me to grab the first three characters of the "roomnum" property?  something like: - left\$(PRP:"ROOMNUM"),3

Any help would be appreciated.