Sink or swim, eh? :)
I'm not really sure how much of this I should describe. You really need to start looking into some books about object oriented programming, particularly in relation to Access.
A quick overview...
In object oriented programming the terms are pretty self-descriptive. For example, an Object is a thing that is more-or-less "tangible". A form is an object. A combo box on a form is an object. Each object has Properties. Properties are the characteristics of an Object. The size of the form, height and width, are Properties of the form. The location of the combo box on the form, top and left, are Properties of the combo box. A combo box has the Property "Enabled". Events occur in relation to objects. For example, when a user opens a form, several Events occur for that form. Load and Activate are two of those events.
For the purposes of your code, you're interested in the Load event. So you'll look at the Properties of the form and give the "On Load" Event Property some code. That is a bit confusing. The code is actually a Property of the form. But the code is something that will execute as a result of an Event that occurs in relation to the form.
If you're with me so far...
When you select the dropdown for the "On Load" event property of the form, you'll see "[Event Procedure]". Select that then click the elipse (...) next to it to open the Visual Basic Editor (VBE). You'll see that Access creates the Form_Load event template where you can write your code. Your code will be something like:
Code:
If (CurrentUser = "username1") or (CurrentUser = "username2") then
Me.ComboBoxName.Enabled = True
Else
Me.ComboBoxName.Enabled = False
End If
I'm not clear about what you want to do to "refresh the status with reloading the form". The On Load (Form_Load) event is kicked off every time the form is loaded (i.e. every time a user opens a form in Form mode -- not design mode). So the Form_Load code will run to enable or disable the ComboBox control whenever the form is loaded.
From there you're just going to have to get into this on your own. I really don't know how "basic" I need to be to get you started. And it is difficult to describe all of this without knowing whether you're making the connections. You might try looking at the Northwind sample database for some ideas.
Just have some confidence that you can do this. It really isn't terribly difficult. There's a lot to learn. I seem to learn something new every week and I wrote 4 chapters in "Access 2003 VBA Programmer's Reference". But you don't have to know all of it to do the things you need to do to get started. In fact, I'm amazed that you're tackling the Workgroup File. That was one of the chapters I wrote and Access Security is pretty confusing!