You might look at the administrative control (adminctrl)...I see a few possibilities there such as "resolutionx" and "y"....otherwise, my understanding of the control is that it's fairly generic and may not tell your scanning software how to set the scan resolution. There are two options for this that I can see:
1. See if your scan driver can use a preset; i.e. save your default settings that will be used automatically when invoked.
2. My Visioneer came with activeX drivers (although I haven't used them)...your scanner may have more specific drivers as well.