Head coach Andy Robinson has added the back row forward to his squad after the withdrawal of Scott Newlands.
A product of GHA and the National Academy, the 22-year-old has previously represented Scotland 7s and made a handful of starts for the Warriors last season; earning him his place on the trip to eastern Europe.
Robinson welcomed the new recruit and believes he will make a contribution during the three matches.
Robinson said: “I’ve been impressed with what I’ve seen of Calum so far and Sean Lineen has also recommended him. He is a useful young back row player with plenty of potential and this trip will be a useful experience for him as part of his development.”
Scotland ‘A’ squad for the IRB Nations Cup 2009: Joe Ansbro (Northampton Saints), David Blair (Edinburgh), Kelly Brown (Glasgow Warriors), Ben Cairns (Edinburgh), Stuart Corsar (Doncaster Knights), Geoff Cross (Edinburgh), Chris Cusiter (captain, Perpignan), Simon Danielli (Ulster), Nick De Luca (Edinburgh), Rob Dewey (Ulster), James Eddie (Glasgow Warriors), Calum Forrester (Glasgow Warriors), Roddy Grant (Edinburgh), Alex Grove (Worcester Warriors), Craig Hamilton (Edinburgh), Ruaridh Jackson (Glasgow Warriors), Alastair Kellock (Glasgow Warriors), A Kelly (Edinburgh), Rory Lawson (Gloucester), Scott Lawson (Gloucester), Moray Low (Glasgow Warriors), Alan MacDonald (Edinburgh), Jim Thompson (Edinburgh), Kyle Traynor (Edinburgh), Richie Vernon (Glasgow Warriors) and Simon Webster (Edinburgh).
IRB Nations Cup 2009 (all games to be played in Bucharest)
Friday, 12 June, Scotland ‘A’ v Russia
Tuesday, 16 June, Scotland ‘A’ v Uruguay
Sunday, 21 June, France ‘A’ v Scotland ‘A’