I am trying to narrow down records of students by subject code and time code. I have a parameter query that prompts users to enter the values. Is there anyway that I can have a combo box instead of having users enter the data themselves? Any help would be greatly appreciated.

You can do this, but not directly in the query definition itself. You will have to design a form that will have the ComboBox. You could then use code behind the form to implement your selection criterion in a few different ways. For example, if you are ultimately displaying the info in a report, you can use the VBA code to dynamically set the report's data source SQL statement (the ComboBox selection would be used to define the WHERE clause).

I sometimes go one better by using a multiselect ListBox, and then use code to dynamically build the IN () statement I use in the WHERE clause.