1756 Series and other modules that run on BTR/BTW (Flex, 1771, etc) allow for reconfiguration on the fly.
For 1756, you make the changes for each channel on the scaling or channel tab on the module properties box (while online), and hit apply. You will get a warning that the MODULE may (or will) go offline while the changes are applied, but this really shouldn't hurt anything (unless you are making major changes that will confuse your process).
Programmatically configuring 1756 modules is a bit more complicated, and requires the use of CIP formatted MSG instructions with specific attributes, but works fine.
If you really do have a BTR/BTW module, it's likely that the program is constantly writing a default set of values to the module, so if you try to make a change, it gets tossed away. If that's the case, find the data for the associated BTW, and write the scaling values in there.