If you make a form based on your employee table and in the form header
put a textbox to hold the given date then on the body of the form you can
put an unbound text box called say "txtShiftCount" and in the form's On
Current event handler put code like:

Private Sub Form_Current()

   Dim db As DAO.Database
   Dim rs As DAO.Recordset
   Dim str1 As String

   Set db = Application.CurrentDb

   str1 = "SELECT Employees.Employ_Ref, Schedule.ScheduleDate "
   str1 = str1 & "FROM Schedule INNER JOIN (Employees INNER JOIN "
   str1 = str1 & "ScheduleDetails ON Employees.Employ_Ref =
ScheduleDetails.Employ_Ref )"
   str1 = str1 & "ON Schedule.ScheduleID = ScheduleDetails.ScheduleID "
   str1 = str1 & "where Employees.Employ_Ref = " & CStr(txtEmploy_Ref)
   str1 = str1 & " and Schedule.ScheduleDate >= #" &
CDate(ScheduleDatetxt ) & "#"

   Set rs = db.OpenRecordset(str1)
   rs.MoveLast
   rs.MoveFirst

   txtShiftCount = rs.RecordCount

End Sub

then that should populate the unbound text field with the correct count.
You should add the same code to the after update event handler of the
ScheduleDatetxt  textbox and make sure that textbox is formatted as date.

Doug