If you upgrade a copy of ERPlite that has custom changes, the custom changes will be lost. Thus, you should have a backup copy, plus a plan for porting the changes to the new ERPlite release.
The ERPlite Release Notes document the major changes in each release of ERPlite. Thus, if the object that you customized (say the Purchase Order ) was not changed, then you can simply import (file > get external data > import > the custom object from custom frontend).
Another userful tactic, is to put custom objects in a separate Access database linked to the backend datafile.
Last, but not least, keep a set of notes so that you can easily redo the changes.
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