Hi Larry,
Are you using a single form with multiple views? You can do this pretty easily with a single form and multiple views. The inital page your user would open would be the first view of the form where they would select their diagnoses. Then, when they have made all their selections, they would click on a submit button that would open a 2nd view of the form, but only displaying the selections they had selected on the previous page.
One way to make this work would be to make all the selections on the first view check boxes, but make them Text(String) check boxes (the default is boolean (True/False)). Then in the area where it says "When Value Checked" you would put the diagnoses that this check box corresponds to on the form. When the user makes selections in the check boxes, those values (diagnoses) are available to display or not display in the next view (or other views) in the same form. In other views you can then display the value of the selection in a text box or an expression box AND here you create a rule that says to hide the control if the value is blank (that the user didn't select it on the previous view).
Make sense?