[b]VCCS for 558 one shot[/b]? PLS Help!

I need a way to control the pulse width of a 558 one shot using voltage. At first I thought I could use a voltage controled resistor, but everyone has suggested using a voltage controled current source instead of a RC circut.

I know nothing about voltage controled current sources. Can anyone help? Any good websites for reading up on these? Can anyone recomend any schematics?

Thanks for any help. If I can get this a long term project will be done.