If you want to dynamically change layout sizes for example you need legal size and sometimes you need letter size.
It is very simple to do. In MS Word, you create a section break every time you have a different layout size. In the example below there will two sections, one for legal and one for letter size. In each section you code it like this:
<?if@section:P_SIZE='LEGAL'?>
<?if@section:P_SIZE='LETTER'?>
<< ---- y o u r l e t t e r s i z e l a y o u t ---->>
Understand that the coding above resides in the respective section. P_SIZE is a parameter defined in the data model but it could be anything.
I want to give credit to Vishal Pathak for posting this on his blog.