Open the Geographic Calculator.
Go
to Options 
Linear Unit
Definitions... or use the 
button.
The Linear Unit dialog will appear.
Select
the 
control
button.
Linear Unit Definitions...
Follow these steps to create a user defined linear unit:
Open the Geographic Calculator.
Go
to Options Linear Unit
Definitions... or use the button.
The Linear Unit dialog will appear.
Select
the control
button.
User will be prompted to enter a Unique Unit Name for the linear unit.
Enter LEUCARUM-HISPANICARUM for the unit name. The linear unit is automatically copied to the name box.
For the description, enter the phrase "Spanish League".
In the edit box labeled suffix, enter lh. This is the ID abbreviation that will appear on the unit control button on the Geographic Calculator interface when the linear unit is selected.
Enter the value 6300 in the edit box labeled Conversion Factor (to 1 meter).
This is the number of meters per LEUCARUM-HISPANICARUM (i.e. 6300 meters = 1 lh).
Click the Save control button.
The definition is now entered into the geocalc.dat database, and can be selected from the linear unit drop box.
(Linear Unit Definition Dialogue)