Boolean Tri State for filter table

Boolean parameter tristate, options for listbox completion field to select are yes, no, all. Would imagine the actual values would be 0 -1 and null , is this correct?


If you are checking it from a form the values are:

 0 = Not Selected
 1 = Selected
 2 = Not Defined

Checking the value from a query:

 0 = Not Selected
 1 = Selected
 NULL = Not Defined

Thank you very much for this, now to put the options into a filter listbox i guess I need to set up some dummy table aka id pk,state varchar Yes, No, All, and the stored field to be lets say value integer.
Once again appreciate your help.