Check a file's save status.

Ok, this seems like it should be simple, but I'm trying to do a simple check if a file has been saved or not at the beginning of my applescript. 

I tried just putting a consistent save at the beginning, but I'm working with big files and if they've already been saved it's a big waste of time to sit there and wait for them because they always save. 

The basic set up i want is:

if theFile is not saved

     save theFile

else

end if

i just cant figure out the wording and I cant find it in any of the references.