I don't think its possible. You can get an adapter to down convert from DVI->VGA (one example of this came with 15 and 17" Powerbooks), but not one to convert up from VGA->DVI.
In addition to what I said above, even if you could find some way to convert the VGA signal to DVI, you'd still need Apple's DVI to ADC converter, which is about $100.
That monitor has a DVI-I port (both digital and analog) and the Samsung site says it accepts an analog RGB signal, so you should be able to get a DVI > VGA cable (if it doesn't come with one) and use it fine on your iBook. If the website is wrong and it does need a DVI/digital signal, then that's already been answered in this thread. you need a VGA>DVI converter, which will run you about $300.