[Thak2]

make a bigmap.txt file with the level names in the order you want them. Like:
"levela1.graal","levela2.graal",
"levelb1.graal","levelb2.graal"

save it in the folder with you levels, then right click on one of the levels you want mapped, click on Open With, and open it with graal.exe, then in the editor hit "M".