I have changed block sizes several times. What I do, is print out the pattern. Using the chart I have included here, find the % change you will need to make. Using a calculator, go through the block measurements and change each number to reflect that % change. This coincides with Scissor Queen's response. It is a matter of reducing or enlarging each part of the block to get to your end result measurement.
Going from 14" block down to 10" block is simply reducing your measurements to 71% of each #. When I can square up, I try to make sure my measurements are a tad over what is called for.
http://www.thequiltedsnail.com/scale.html