The key is to have the option Both evaluate the where clause to be
Code:
{MyStatusField] Like "*"
Your combo box with the three values, Open, Closed, & Both needs to have two columns. The bound column will return "*", "Open", or "Closed"
If using a form reference Your query would look something like this:
Code:
{MyStatusField] Like forms!MyFormName.cboMyStatusControlName
The combo box properties are:
Column Count: 2
Column Widths: 0";1"
Bound Column: 1
Row Source Type: Value List
Row Source: "Open";"Open";"Closed";"Closed";"*";"Both"