Changing IFRAME Source Dynamically from inner script

[Herbman]

I have an HTML document with two <IFRAME> tags

<iframe src='Page1.htm' name='frPage1' width='241' height='322' </iframe>
<iframe src='Page2.htm' name='frPage2' width='241' height='322' </iframe>

I would like to write some script inside the source of the first IFRAME object,
namely Page1.htm, such that it can change the source of the second IFRAME
object.

Does anyone know how to do this?

Thanks A lot.

herbman