Whenever you can enter a numeric expression using the calculator, you can specify a parameter instead.
To use a parameter:
button. Alternatively, right-click a text box in the current dialog to display the Calculator dialog.
You can also create and use a parameter by typing directly into a text box on a dialog or toolbar. For example, type:
param_name = value
where param_name is the name of the parameter and value is the numeric value of the parameter.
The type of parameter created is determined by the function of the dialog or toolbar.