Editing Check Constraints
You can change the expression of a check constraint using either of the approaches listed below. When you take this action, note that the check constraint is deleted first and then recreated with the new definition.
From the Online Browser
1.In the Online Browser, select a check constraint from the "Check Constraints" folder of a table.
2.Enter the new expression in the Expression property of the Properties window. A structure change script is generated automatically in the Database Structure Change Script window.
3.Click the Execute Change Script 
button in the Database Structure Change Script window.
From the Design Editor
1.In the Design Editor, select a check constrains from the "Check Constraint" section of a table design.
2.Enter the new expression in the "Expression" column. A structure change script is generated automatically in the Database Structure Change Script window.
3.Click the Execute Change Script button in the Database Structure Change Script window.