Page on Load

Dieter,
there is no reliable method to do this.
Here is the rough method for achieving the next ID.

Put this code into AddOnLoad event:

global $conn;

$rs=db_query("select max(ID) from YourTable",$conn);

$data=db_fetch_numarray($rs);

$nextid=$data[0]+1;

echo "The next ID is ".$nextid;

where YourTable and ID are your actual table and field names.