That should work. You can simplify your code a little:

DoCmd.OpenForm "frmCourseDetails",,, "CourseID=" & CourseID

(I can always tell when people learned from me or somewhere else just by how you write code. LOL)

But yes, if the form is set to Data Entry then you'll have to change that.

Humm, I was hoping that was not the answer.

I want the main form, when access to open to form entry, but if the user accesses via the assignment sub form I wanted it to take them directly to their assignment.

Set Data Entry to no. If you open it from whatever other menu form you're using, just set the Data Entry property in the OpenForm command (it's one of the parameters). See Data Entry.

LOL, I tried that but then it negates my search function on the main form if they want to search for a record.
Can I have two forms with the exact information? Let's say the main form and then an update form and I would link my update form to the sub form?

You *could* but that's not very elegant. I'd really have to see more of what you've got going on there to tell you for sure. Screen shots would help.

Ok I will try to chunk out what I am doing.
My course details form is the main form, when you open it you can enter new course details or search for an existing course. I set this main form to 'On Load' new record. That way someone would not accidently edit the first record.
The data base is used by a verity of people on the project.
What the team asked for was to link the course and event assignments to the contact.
I created a subform based on an assignment query I created.
I added that assignment subform to my contacts form as a tabbed sub form.
Now the user can lookup their name and see all their assignments for the project.(works)
What I want to do from there, is link the assignment ID back to the main form, but because I have my main form set to new record on load it does not go the the specific record on the main form. It does exactly what I told it to do,LOL, loads to new record.
If I take the on load function off it works perfectly, but that leaves the first record open to ac

Set the main form to visible or invisible as you see fit.  Don't use On Load, since it doesn't serve your purpose in this case.  Keep the main form "opened," but set its visibility with VBA when needed.  That would serve your purpose of preventing others to see your main form perfectly.  Invisible forms and controls can still be controlled with VBA.  They just can't get focus.  Use SetFocus on them and you get a run-time error.