Change Focus for TextBoxes using Javascript

In most of the real time project there will be requirement to change focus of the TextBox from one to another dynamically, instead of clicking the TextBoxes. The ideal example in this case would be Phone Number Text Boxes in the US format(000-000-0000). Consider there were three TextBoxes. It wil be irritating for the end user to click each text box and then type numbers.So here, on every