I'm not sure how you build your drop downs but at http://www.pcpropertymanager.com's order page I ask people what OS they have and what country they are from.
If the visitor submits without completing another part of the form the page returns with the OS selected. As the list is limited in range (ok, countries is a long list but it is finite) I have given each item on the list it's own template code then used phplib's template to set a variable. The variable is probably just {win95sel} which is $ostype . "sel"
The template then says that it doesn't have a value for the others so it strips out the unwanted text between the curly brackets. works like a dream.