I have a range finder but I rarely ever use it when hunting squirrel. If you are using a separate device to range and then adjusting your scope before shooting, it's no surprise that the squirrel is gone by the time you are ready.
Even if you got the two in one range fiber / binoculars, I think you'd still have this issue.
Like Addertooth said, a decent scope with good ranging would solve the problem in the best way.
As an alternate suggestion, get familiar with the area you hunt in and use the range finder to identify the distance to a few key reference points around you before you start looking for squirrels.
Also, if you haven't already, try zeroing the scope at the most common distance you take hunting shots. Then, for any game that is within 30 yards of your zero (15 yards up or down), you can just point and shoot without worrying about the correction.
The only time i have time to make adjustments when squirrel hunting is when I spot them just sitting still on a branch, which is not often and they are better at spotting me than I am with them (so they don't stay still for long).