Main Form: frmProjects (underlying tblProjects)
Subform on Main Form: frmManagers (underlying tblManagers)
Fields for frmManagers: [cboMANAGER_ID], [STARTDATE], [ENDDATE]

Problem: How can I ensure that there are no overlapping periods where one manager is assigned
to a project?

Example: Manager 1 04/04/04 to 04/04/05
Manager 2 04/05/05 to 08/05/05
Manager 3 06/05/05 to 12/05/05

I would want to prevent Manager 3's start date from being entered and display an error message
because it is included in the assignment period for a previous manager.

Thanks for your help.

Hi -

Take a look at Allen Browne's excellent article on clashing events.

HTH - Bob