boom = "heat105" camcreate [(getpos player select 0) + 2, (getpos player select 1) + 1, getpos player select 2]
this will create (I think) a heat round 2 metres along the x axis from the player and 1 metre on the y axis.
however, a heat round this distance away is most likely to blow the player apart. instaed, if it's for effect only, use a handgrenade ("grenade"). also if you place it slightly underground (the z axis), then the exlplosion doesn't spread as much but you still get the explosive effect (try a couple of metres underground)
EDIT: of course if it's a heat 120 round use "HEAT120". Forced to edit as i know someone will be pedantic and point that out!!!