Containing A Date Textbox And A Submit Button And A Close Window Button?

I have a form containing a date textbox and a submit button and a close window button. The date textbox onblur calls a javascript function which checks for date validation and some other logic and displays some alert messages. The date on the textbox is always selected and onfocus. My problem is when I try to click the close window button with/without changing the date the alert messages from the onblur logic are displaying and I am unable to close the window. I tried using onchange instead of onblur but onchange too works when a control looses focus. it works fine when I donot change the date but when I change the date and hit the close window button it too displays the alert messages and the window does not close. Please suggest me what will be my best option.