In the iSupplier Portal when the user selects a Product and Services category, can I make the select

In the iSupplier Portal, when the user selects the Products and Services category can I make the selection of Sub-category mandatory? Thus, the user would not be able to select the first segment of the category alone, but would have to select the sub-category. I have defined the Products and Services with two segments and both are mandatory in the flexfield category setup. The ''POS: Product and Service Segment Definition' is setup as 1.2 to enable both categories. I am now able to see the sub-category in iSupplier portal, but the user is allowed to just select the main Products and Services level without navigating to the sub-category level, whereas we want the user to select the sub-category level.