I don’t think it exists. The only thing I can think of is sacrificing another project info field for this purpose, and making sure you enter a hyphen there if the two other fields are not empty.
I had a method for a very similar question just today. This is slightly easier: You can put the dash (& spaces, whatever) in the field that’s used only sometimes.
I would welcome a new token or function for this (fairly common) purpose – that appears only when the tokens on either side of it are not empty.