What is the story behind your problem? Is it a form where you use a "save"-button, or do you use a save action on an onChange action?

There is one more Combo box where if I change the selection ,(So on change of combo box selection) I need refresh values in other combo boxes like set them to default..

So you are using an onChange action. In that action, you can use the assign to assign the defauld value to combo box 2 when combo box 1 changes. After that assign, you can use an Ajax refresh to refresh only combo box 2 (this way you don't have to reload the whole page). 

I need to know how to set it to the Combo box 2 to Value1 0 and Option1 Select ehrn I change the Combo box 1. I am not sure how to set that...