Are you getting an error or just no data returned?
try this
$sql = "SELECT * FROM users WHERE upper($field) LIKE'%".$find."%'"
die($sql);
$data = mysql_query($sql);
Looks like you put the find variable inside of single quotes which treat it as literal. mysql is looking for $find and not the contents of that variable.
The die function will exit the script and echo out the query, if it looks good then comment out the die and continue.