I got the solution. I was writing the script("this.assist.toolTip.value = this.rawValue;") on "mouseEnter" event but need to write script on "Exit" event of the field. Thank you.

Is there any way to display dynamic value in tool tip?I have tried:        this.assist.toolTip.value = this.rawValue; for a text field on "mouseEnter" eventbut it is not displaying the current  raw value. It is displaying previous raw value of the field..I have written 'AAAA' but it is not displayin...