well, it depends on which details u wanna check, however, a general approach is to first check whether there r already records that match your details. i.e., if u store a title or name with the course, u could use something like this:
$query = "SELECT * FROM courses WHERE name='$name'";
$result = mysql_query($query);
if(mysql_num_rows($result) > 0)
{
// display error etc.
}
else
{
// add entry
}
assumin $name has been submitted by a user usin your form, this code checks if there are already similar entries available, so that you can output an error message. combinin this name check with a date check, u should not encounter further problems - use a query string like $query = "SELECT * FROM courses WHERE name='$name' AND date='$date'";
hth
