If you really really really can't find a helper.... there are dial indicators which can be clamped in place which will " keep" the max reading they get... like thermometers for greenhouses can do....
They are the cat's meow.... but are expensive.... and likely most people at the desk won't even know what you are talking about...
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edit...ok... found this better name for it..

"One more related feature is "hold/reset." This is used primarily where the readout is difficult to observe; for example, where the entire gage is inserted into a part to measure an awkwardly placed internal dimension. The hold feature allows the indicator to retain the reading so that the operator can extract the gage and view the readout, then clear it with a reset button."
from:
http://www.findarticles.com/p/articles/mi_m3101/is_n4_v66/ai_14469677