Ah since you're referencing them by name instead of their number you should put " marks around them, eg: "c1". Otherwise you can reference their layout number exactly (c1 would be layout 3 I think, unless it's 0-based then it would be 2).
Going by name lets you do things like: Go to layout -> "Level" & (global('LevelNum') + 1)
Edit, as a further example you can also bring randomness into it: Go to layout -> "Level" & clamp(random(3) + 5, 5, 8)
This would go to a level between Level5 and Level8
Hope that helps! <img src="smileys/smiley1.gif" border="0" align="middle" />
Double Edit: Oops, did the math in my head wrong, this would only spit out Level5 to Level7, thanks Tulamide! <img src="smileys/smiley9.gif" border="0" align="middle" />