Validation of Edit Control

Hi, I have created a dialog-based program with an edit control (range specified in class wizard) and a timer running when the program starts. The timer will update a static text in the dialog. I have attached the EN_ENABLE to the edit control and added the code UpdateData(TRUE).
An error occurs when I key in a value outside the specified range of the edit control. I guess it is due to the timer trying to update my main dialog when it becomes inactive due to the present of warning message box stating that a value outside range has been keyed.
I have tried for a long time but was unable to solve the problem. Will anyone please help me with the problem? Thanks in advance.

Regards..
.........Jon Min