I acutually want to add text to a hidden field, but I am using a text field for testing - if that makes a difference.
Code:
Page A

<script>
window.open('testB.htm', 'CtrlWindow', 'width=300,height=250,top=100,left=200,toolbar=no,menubar=no,location=no,scrollbars=no,resizable=no');
</script>
<form name="TestForm">
	<input type="text" name="TestField" size="20" value="1 2 3">
</form>


Page B

<script>
	opener.window.documnet.TestForm.TestField.value = opener.window.documnet.TestForm.TestField.value + "4 5 6";
</script>
Thanks -