update mysql problem

[roman_dolan]

Heres my problem

I have a MySQL table with a subset of results available to the user.

Each row of this subset has a sequential number indentifier 1,2,3 etc.

The user can delete 1 or more rows via a html form

so say he owns 4 rows of the table and deletes his 3rd row.
This would leave him with rows with 1,2,4 identifiers

I need to reset the identifiers to 1,2,3.

and Im really struggling with this.

Im not sure if I've explained this at all clearly
but if anyone has solved (this apparantly trivial) problem please clue me what to do

Many thanks

[laserlight]

How are your tables structured?
There might be a better solution to your problem.

[roman_dolan]

Table structure is

CREATE TABLE activity_list (
user_id varchar(12) NOT NULL default '',
dept varchar(20) NOT NULL default '',
section varchar(20) NOT NULL default '',
act_code varchar(12) default NULL,
act_desc text,
date timestamp(14) NOT NULL,
KEY act_code (act_code),
KEY user_id (user_id),
KEY section (section)
) TYPE=MyISAM;

where user id, dept, and section defines the sub table
mentoned in first post and act_code field contains the
sequential identifier
1,2,3 etc