I am stuck on something that should be really basic...
I have a form I would like to place a ComboBox in the header to select a Uniform Item, and display all orders in the detail part of the form through a subform.
:banghead:
instead of opening a subform why not open a report based on your selection. If the issues is with the results that are returning then ask yourself what is missing and why. It could be the query used in the combo box or form is using the wrong Join type. If the form is based on a query does the query return the dataset correctly in the query view? But like Mark said you did not state what the issue is.