My guess is, that it would be possible using an identity column, but I wouldn't go for that if it needs to be reset on a daily basis.
It's probably me, but I'm still not quite clear on what you want, on the other hand, maybe I do but miss the point as to why you need a linenumber associated with the table contents.
One of these might work for you though:
- create a view that has a computed column (if the linenumber can be determined on other information from the table);
- create a trigger that does an update (guess this can be quite a burden);
- create an sp; do an update based on identity from a temp-table.