I'm sorry that the above suggestion doesn't work. I list the script for your inspection.
Private Sub chkR1_1_Click()
Dim dDtTeach1, dDtTeach2, dTeach1, dTeach2 As Date
Dim sSelectDt1, sSelectDt2, sProgram As String
Dim iRotation, iSession, iSCnt As Integer
Dim iSession1...