I see that you are looking for a way to manually tweak the fan spin on your Intel(R) Desktop Board DZ68BC.
In regards to your inquire, the fan control cannot be tweak in BIOS to set specific speeds, but using the Intel® Extreme Tuning Utility, you will be able to set the fan control a little more specific.
You can download this tool from the following web site:
The link behind the text is incorrect, so I'll link it for anyone interested:
This raises a couple questions: Shouldn't v3.0 work on this board? Also, while I don't see any actual documentation for this program, the page makes mention only of monitoring fan speeds. Is that correct?