Looks like monPos is not a function, but an array. Is it a scope issue?
IF newLevel = 0 THEN LET newLevel = 1 LET numberOfMon = 50 LET toggleFirst = 0 LET toggleSecond = 0 LET scrolly = 0 LET scrollx = 0 DIM world$(10000) DIM tile$(10000) DIM colAmain(10000) DIM colBmain(10000) DIM colCmain(10000) DIM colA(10000) DIM colB(10000) DIM colC(10000) DIM monsterPositionPlace(numberOfMon) DIM monChar$(numberOfMon) DIM monColA(numberOfMon) DIM monColB(numberOfMon) DIM monColC(numberOfMon) DIM monName$(numberOfMon) DIM monLife(numberOfMon) DIM monAttack(numberOfMon) FOR a = 1 to 10000 LET world$(a) = "#" LET colAmain(a) = 150 LET colBmain(a) = 150 LET colCmain(a) = 150 NEXT LET roomsStart = 5550 LET nextRoom = roomsStart FOR a = 1 to 18 LET nextRoom = nextRoom - 1 LET createFloory = nextRoom IF a = 6 THEN LET nextRoom = roomsStart LET nextRoom = nextRoom - 1 END IF IF a = 12 THEN LET nextRoom = roomsStart LET nextRoom = nextRoom - 1 END IF FOR b = 1 to 5 IF toggleFirst > 0 THEN LET createFloory = createFloory + 100 LET nextRoom = createFloory + 100 END IF LET toggleFirst = 1 LET createFloorx = createFloory LET nextRoom = createFloory FOR c = 1 to 5 IF toggleSecond > 0 THEN LET createFloorx = createFloorx + 1 LET nextRoom = nextRoom + 1 END IF LET toggleSecond = 1 IF createFloorx > 100 THEN IF createFloorx < 9900 THEN LET world$(createFloorx) = "." LET colAmain(createFloorx) = 150 LET colBmain(createFloorx) = 150 LET colCmain(createFloorx) = 150 END IF END IF NEXT NEXT LET hallDir = RANDOM(4) LET createHall = nextRoom FOR d = 1 to 22 IF hallDir = 1 THEN LET createHall = createHall + 1 LET nextRoom = nextRoom + 1 END IF IF hallDir = 2 THEN LET createHall = createHall - 1 LET nextRoom = nextRoom - 1 END IF IF hallDir = 3 THEN LET createHall = createHall + 100 LET nextRoom = nextRoom + 100 END IF IF hallDir = 4 THEN LET createHall = createHall - 100 LET nextRoom = nextRoom - 100 END IF IF createHall > 100 THEN IF createHall < 9900 THEN LET world$(createHall) = "." LET colAmain(createHall) = 150 LET colBmain(createHall) = 150 LET colCmain(createHall) = 150 END IF END IF NEXT NEXT // PLACE MONSTERS FOR monPlacer = 1 to numberOfMon LET monsterPositionPlace(monPlacer) = RANDOM(10000) IF world$(monsterPositionPlace(monPlacer)) = "." THEN LET RND = RANDOM(3) IF RND = 1 THEN LET monChar$(monPlacer) = "g" LET monColA(monPlacer) = 150 LET monColB(monPlacer) = 70 LET monColC(monPlacer) = 70 LET monName$(monPlacer) = "Goblin" LET monLife(monPlacer) = 22 LET monAttack(monPlacer) = 9 END IF IF RND = 2 THEN LET monChar$(monPlacer) = "s" LET monColA(monPlacer) = 70 LET monColB(monPlacer) = 70 LET monColC(monPlacer) = 150 LET monName$(monPlacer) = "Snake" LET monLife(monPlacer) = 12 LET monAttack(monPlacer) = 7 END IF IF RND = 3 THEN LET monChar$(monPlacer) = "r" LET monColA(monPlacer) = 150 LET monColB(monPlacer) = 70 LET monColC(monPlacer) = 150 LET monName$(monPlacer) = "Rat" LET monLife(monPlacer) = 5 LET monAttack(monPlacer) = 4 END IF END IF NEXT LET scrolly = scrolly - 360 LET scrollx = scrollx - 290 LET playerPos = 5550 LET posYcounter = 10 LET posXcounter = 10END IFFOR b = 1 to 10000 LET colA(b) = colAmain(b) LET colB(b) = colBmain(b) LET colC(b) = colCmain(b) LET tile$(b) = world$(b)NEXTLET colA(playerPos) = 420LET colB(playerPos) = 420LET colC(playerPos) = 420LET tile$(playerPos) = "P"FOR a = 1 to numberOfMon LET monRNDmove = RANDOM(4) IF monsterPositionPlace(a) > 100 THEN IF monRNDmove = 1 THEN LET monsterPositionPlace(a) = monsterPositionPlace(a) - 100 IF tile$(monsterPositionPlace(a)) = "#" THEN LET monsterPositionPlace(a) = monsterPositionPlace(a) + 100 END IF END IF IF monRNDmove = 2 THEN LET monsterPositionPlace(a) = monsterPositionPlace(a) - 1 IF tile$(monsterPositionPlace(a)) = "#" THEN LET monsterPositionPlace(a) = monsterPositionPlace(a) + 1 END IF END IF END IF IF monsterPositionPlace(a) < 9900 THEN IF monRNDmove = 3 THEN LET monsterPositionPlace(a) = monsterPositionPlace(a) + 1 IF tile$(monsterPositionPlace(a)) = "#" THEN LET monsterPositionPlace(a) = monsterPositionPlace(a) - 1 END IF END IF IF monRNDmove = 4 THEN LET monsterPositionPlace(a) = monsterPositionPlace(a) + 100 IF tile$(monsterPositionPlace(a)) = "#" THEN LET monsterPositionPlace(a) = monsterPositionPlace(a) - 100 END IF END IF END IF LET colA(monsterPositionPlace(a)) = monColA(a) LET colB(monsterPositionPlace(a)) = monColB(a) LET colC(monsterPositionPlace(a)) = monColC(a) LET tile$(monsterPositionPlace(a)) = monChar$(a)NEXTCLEARPRINT "Press the spacebar key, type lower level then press the enter key to go to the next floor down"PRINT " "FOR a = 1 to numberOfMon IF playerPos = monsterPositionPlace(a) THEN LET life = life - monAttack(a) LET monLife(a) = monLife(a) - attack PRINT monName$(a) + " attacked you" PRINT "Your life is now " + STR$(life) PRINT "You Attacked " + monName$(a) + " for " + STR$(attack) END IF NEXT