To Edit a Custom Units System
To redefine a units system that you previously created,
1. Click File > Prepare > Model Properties. The Model Properties dialog box opens.
2. Click change in the Units line. The Units Manager dialog box opens to the Systems of Units tab.
3. Double-click the custom units system you want to edit, or select the system and then click Edit. The System of Units Definition dialog box opens.
4. Redefine the units system as necessary, and then click OK to close the dialog box.
5. Click Close to close the Units Manager dialog box.