为什么不在网页中调用javascript函数？

There are two textboxes (txtTimeFrom and txtTimeTo) for a time period in a webpage using a asp.net Master page. I used a javascript to validate the data a user enters in these two boxes as a date type on TxtTimeTo onBlur event then call TextTimeTo's code behind event TextChanged to access SQL to get data.There are two textboxes (txtTimeFrom and txtTim