Here is a useful bit of information about Character Ranges (classes are covered as well):

http://lua-users.org/wiki/PatternsTutorial

Here is how you can quickly check for say the number five (5) is between a range of numbers):

Code:
-- First define a variable to hold a random number to check against
n = 5

-- Note 'string.find' is all lower-case!  It's a LUA function (not AMS created)
result = string.find(n, '[1-8]')

--[[
If there is an instance of '5' between 1 and 8, then show confirmation...
otherwise, show the second (no instances found) dialog.  This is a good way
to easily check a "range" of numbers!  Forum member Tigger first alerted us
to this LUA innate function.  Remember, type 'string.find' in all lower-case...
or the function will not work!
]]
if result then
	Dialog.Message("", "Found at least one instance!")
else
	Dialog.Message("", "Did not find any instances!")
end