Here's what I have in the Form Code:

Private Sub ChkSelectAll_Click()

    If Me.lblChkAll.Caption = "Select All" Then
        Me.lblChkAll.Caption = "Clear All"
        CurrentDb.Execute "UPDATE ScheduleT SET LnSelect = True WHERE ScheduleStartDate= #" & Forms!RescheduleMultipleEventByWeekF!WeekDate & "#"
    Else
        Me.lblChkAll.Caption = "Select All"
        CurrentDb.Execute "UPDATE ScheduleT SET LnSelect = False WHERE ScheduleStartDate= #" & Forms!RescheduleMultipleEventByWeekF!WeekDate & "#"
    End If
    
    Me.Requery
    
End Sub

Are you trying to select all of the events in the form that are scheduled during the calendar week of the date selected or just all of the events scheduled for a week starting with the date entered?

First Day of Week shows how to get the first and last day of the week based on a date. So you could use that methodology to adjust your SQL to your needs if you want a calendar week. Otherwise, it would just be between StartDate and StartDate + 7.

Your SQL in the first method, your SQL might look like:

CurrentDB.Execute "UPDATE ScheduleT SET LnSelect = [TrueFalse] WHERE ScheduledStartDate Between #" & CalculatedFirstDayofWeek & "# AND #" & CalculatedLastDayofWeek & "#"

The second way might look like:

CurrentDB.Execute "Update ScheduleT SET LnSelect = [TrueFalse] WHERE ScheduleStartDate Between #" & Forms!RescheduleMultipleEventsByWeekF!WeekDate & "# AND #" & Forms!RescheduleMulptipleEventsByWeekF!WeekDate + 7 & "#"

Keeping in mind: Between includes the first date and ends 11:59pm on the date before the end date. Also, in my examples, replace [TrueFalse] with the appropriate value in the applicable part of your sub. Also, as your code is presented, it indicates that there is an "LnSelect" field in the underlying table, otherwise it won't know what you're trying to do.

Thank Donald, you are right. I was going about it all wrong. Thank again!!!