Copying Textbox values in Gridview with Javascript

I am trying to accomplish the following in a GridView that has one
TextBox:

When the person types in a number into the first row (i.e. 100), I
want to use some Javascript to automatically fill the TextBoxes in the
remaining rows with the number incremented in each row (i.e. row 2
will have 101, row 3 will have 102, etc).

My command over Javascript is minimal, so any code examples would be
greatly appreciated.

Thanks!