Sorry for late reply..
I need to check that web edit box should take only characters.Allowed characters are between A to Z and numerical and alphanumerical value is not allowed for that edit box..
Ok, now I'm confused. You stated that the edit box will only accept characters between A to Z and numerical characters but alphanumeric characters are not allowed. Alphanumeric characters and characters between A to Z and numerical characters are the same thing.
Simply enter characters that are allowed and verify that no error is generated. Enter invalid characters and verify that an error message is generated