In addition to Chris' reply, I think what you need is a
named access list. So that you change a specific access list entry using its line number. This way, the position is not changed after editing if this makes sense.
e.g.
In global config mode obviously,
ip access-list standard testacl
10 permit ip host 1.2.3.4
20 permit ip host 1.1.3.4
30 permit ip host 1.3.3.4
So, to edit the second entry you just do like so:
ip access-list standard testacl
no 20
20 permit ip host 3.3.3.3
sh ip access-list to see the change
what's more, you can even insert an ACL in a particular position without changing any existing entry like so:
ip access-list standard testacl
10 permit ip host 1.2.3.4
15 permit ip host 2.4.5.6 <==new line inserted
20 permit ip host 1.1.3.4
30 permit ip host 1.3.3.4
The numbers are the line numbers i think they are called.
hope this helps
"...you are never too old to learn" anon