How to dynamically react on different parameter counts?

[eluser]Comanche[/eluser]
Ok,

after thinking about it a lot of time I chose to do it the following way:

I just take one parameter which describes which letter was chosen and what the sort order should be and a second parameter which holds current page number.

Letters are enumerated from 1 (A) to 26 (Z) and from 27 (0) to 36 (9), 0 means, that no specific letter was chosen.
To change the sort order I add (or subtract) 100 to (from) this value.

For example "25" means "show entries starting with Y, order ascending" and "125" means "show entries starting with Y, order descending". "0" means "show all entries, order ascending", "100" means "show all entries, order descending".