If you need to define a temporary deviation from the standard tolerance levels, you can change the dimension type on your plan to "deviation".
There are three dimension types (found in the slideout on the plan creation page when you click any given spec). Standard, manufacturing, and deviation.
If you select type "deviation", you can then change the plus and minus tolerances to the required level. Once changed, the plan and inspections will now show that this spec is of dimension type "deviation":
Parts measured will now be subject to the new tolerance levels. As long as the measurement falls within these new limits you will get the usual green "in-spec" indicator. Once you no longer need this deviation applied to your inspections, you can return to the plan and switch the dimension type back to "standard" and revert the tolerances.
The deviated inspections will not change back or show that the measurements are out of spec when you revert the plan.