Dynamic workflow initiation screen

System

TS 6.1 Win2K SP4

I need to modify the default configurable author submit workflow; the requirement is that there should be a list box on the workflow initiation screen and depending on the value in that list box, the rest of the screen should get painted. e.g. If the list box has values 'A' ,'B' and 'C' and if I select 'A' then another list box 'Level 1 Approvers' should get populated with values from a table and if I select 'B' then the same list box should get populated with values from another table.
So the question is, is it possible to repaint the screen and how to go about doing it?
Alternatively, is it possible to achieve this with 2 screens. i.e. on first screen I show only the list box and then on submit I display another screen with data from relevant tables.

I need to do all this BEFORE the job specification is prepared as the values selected in abovementioned screens will be used to generate the job spec.

TIA