Remove special characters from a column

I have column that is only allowed to contain letters, numbers, and spaces. Right now I'm doing several "find/replace" tasks to remove all the special characters (find a comma, replace with nothing; find a pound sign, replace with nothing, etc)...

Is there a formula I can use to clean up the cell value of all special characters, leaving only letters, numbers and spaces? I've tried to google this and found some people using "trim" and "left" functions, but my characters are located at random places that vary from cell to cell, so that won't work for me.

I recommend using a UDF (User Defined Function) such as the one at...
http://stackoverflow.com/questions/1...-period-and-sp