If you want to extract all values from a specific interval from a dataset, you can use the Event Isolation wizard (menu New > Filter) and change the proposed Level Crossing event (by double clicking) to Values in Interval. Enter the lower and upper limits (considering the percent setting).
When you have a signal (e.g. Y component measured over time (as X component)) you can use the Value Index Operator to extract that part where X varies from 0.2 to 100 with
This expression can be used in a formula or as embedded FPScript in data specifiers of diagrams, etc.