Shell Programming and Scripting

I have files coming to an input directory every few mins...eg

test_00012.txt
test_00013.txt
test_00014.txt

I need to write a script to monitor these and if a file is missing from the sequence I need my script to spot this so I can alert someone...

ie... if I got the following:
test_00012.txt
test_00014.txt
test_00015.txt

I am missing the file with seq num... how do I spot this in a script so I can alert it?

Hi ,
one suggestion,
cut the sequence numbers from the first and last file names after sorting file names, somthing like this

1) ls -lrt *test*|sort (seq no.)| cut the seq no. of first and last using head and tail.
2) get number of files by subtracting last and first no.
3) get the no of files using ls -lrt *test* |wc -l
4) compare the result in step 2 and 3.
5) If they are same everything is fine otherwise somthing is missing

Gaurav