There are a couple of ways to do this
For character strings:
* --- Is It In The Search String ---
cThisMonth = "July"
INLIST(cThisMonth,'July','August','September')
or
* --- Is It In The Search String ---
cThisString = 'ABC'
cThisString $ "UYTUYTOILHKGUABCLKLJKJK")
or
* --- Find How Often It Occurs In The Search String ---
cThisString = 'ABC'
OCCURS(cThisString, "UYTUYTOILHKGUABCLKLJKJK")
or
* --- Find Where It Occurs In The Search String ---
cThisString = 'ABC'
AT(cThisString, "UYTUYTOILHKGUABCLKLJKJK")
For numbers
* --- Is It In The Search Number List ---
nThisNumber = 12
INLIST(nThisNumber,1,2,3,4,5,6,7,10,11,12,13,14)
You should look into your VFP Help files for further explanation of each function / operator.
Good Luck