Dependent List Creates Parameter Value Error With Navigation Form

I am attempting to create a customized task manager. I have created a form that has a combo box that list a series of categories. This list is pulled from a query. I also have a sub-category list that is pulled from a separate query. The relevant section of the subcategory query looks like this:

CategoriesID / subCateogiesID
1 / 1
1 / 2
1 / 3
2 / 4
2 / 5
2 / 6
3 / 7

The query has a criteria that sources the combo box on the task creator form. This filters out all other primary categories. I have a macro that auto refreshes the page after the primary category combo box is updated. The sub category combo box then displays the related sub categories.This works great as a stand alone form. However, when I attempt to use a navigation form or use the tab navigation window I get the error message "Enter Parameter Value." I know am getting this message, because the related categories query is looking for a category in the combo box on the form, which at this point in the process is missing. It also does not update once it is moved to a navigation form or tabbed window.