Client Side PropertiesEnable Expression
Description
Enable Expression allows you to enable or disable an input control.
If the Enable Expression evaluates to true then the control is enabled. Otherwise it is disabled. The calculation is performed in the browser using Javascript. You are therefore limited in the use of functions in your enable expression to those functions for which a Javascript equivalent exists.
Clicking the 
next to the Enable Expression property opens the Define Client-Side Enable Expression Dialog. This dialog has additional links to help you in using Javascript Functions, with syntax rules, and in using expressions.