no, it's not.

once again: dosbox has _no_idea_ where the application actually draws the cursor. there's no information "coming back" from the application that would enable this hack of yours, other than screen output. and please don't suggest scanning the screen output for something that might be a cursor

the reason it's not such a problem on a PC is quite simple - the desynchronization occurs just as on the N900, but you don't notice it because the PC's mouse gives relative coordinates.
you might have to move it a little more (or less) to compensate for the desynchronization, but it doesn't "feel" wrong. the mouse may seem sluggish, but it follows where you move it.


a keyboard mouse emulation might be a possibility, but i don't know how much work that would be for javis (a lot, probably)
also, there could already be something like that available, if it runs and works under dos, it may run on the dosbox as well.