The Expression Constraint Settings pane lets you use a more mathematical, and less graphic, method of constraining objects.
Drag the Expression constraint asset into the Viewer window from the Asset browser.
The Navigator window displays the Expression Constraint Settings pane and a new folder named “Constraints” is added to the Scene browser.
Alt-drag assets and devices from the Viewer window and Scene browser into the Expressions pane.
An option appears asking you if you want to create the expression as a Sender or as a Receiver.

Expression as a Sender or Receiver option
Select Sender to create the Expression as a Sender that transmits data.
Each cell contains an object's property as shown in the following figure.

If you select Receiver, you create the expression as a Receiver that is influenced by the data transmitted from the Sender.
Double-click a cell and type a value.
Right-click in the cell and select a new data type from the Data editor to change the cell to a vector or another numerical type.
Edit a cell’s value by dragging left or right to increase or decrease the value.