I have a database that links people by their username in one table to items that they own in several other tables. I am using a form called SearchForm with a Combo Box to display this information. I want to create a form that can house many forms, including SearchForm. Navigation form is what I want to use to complete this. However, when I drag SearchForm to the [Add New] tab in a blank Navigation form template, I get the following message:

This happens every time I try to open the Navigation form called MainForm. I do not get this message when opening SearchForm by itself. I don't even recall ever setting a parameter of Forms!SearchForm!Combo25 anywhere specifically. Of course, if I enter the person's username in this box THEN the SearchForm works inside of MainForm. But this is not desirable. I've looked through the small amount of VB code in SearchForm and I can't seem to figure out how to get SearchForm to work normally inside MainForm.
Here is the VB code that makes the Combo Box work for SearchForm:
Code:
Private Sub Combo25_AfterUpdate()Me.Requery
End Sub
Combo25 operates based on the following query:
Code:
SELECT Users.Username, Users.[Last Name], Users.[First Name], Users.DepartmentFROM Users
ORDER BY Users.[Last Name], Users.[First Name], Users.Department, Users.Username;
There is currently no VB code in MainForm. Could anyone help me out here? I've tried various different variations of Me.Requery. I tried code that makes the subform point to the MainForm with no luck.
Any guidance would be appreciated. Thanks!