The Dell A940 is a rebadged Lexmark X5150 as I understand it, Janni.
See if Lexmark have Mac drivers for this printer. From what I can see the last one for this printer was only compatible with OSX 10.3.9, though, and is shown as not compatible with Tiger. - see
http://www.lexmark.com/lexmark/sequentialem/home/0,6959,204816596666691854_682634834en,00.html
If not see if you can find a "Cups" driver through
http://gimp-print.sourceforge.net/MacOSX.php3 perhaps, though this may only enable the "print" function.
It may be worth bearing in mind that you can probably buy a faster, better, fully compatible, cheaper to run, printer for less money than the cost of replacing the ink cartidges on this 4 year old model, though!
Cheers
Rod