you can use lager malt but if you was trying to copy an exact brew then it will be different but should still be good , are you gonna be using candy sugar ? its easy to make
My dubbel that scored 3rd in one comp last year was without any belgian malt, only Weyermann's vienna, caraamber and abbey (plus some caramelized sugar), Challenger and Styrian Golding hops, but the yeast was true Belgian abbey (Rochefort). Definitely yeast is a key to "belgian character".