Add New Day Number Record And Increase Value By One

I have a table, tblEvents, which I use to store information about a meeting, training session or field trip, including the [StartDate]. I also have a table, tblEventDays, which I use to store the [DayNumber] 1, 2, 3... At the moment I have to enter the day numbers in the subform frmEventDays manually, but I would like to add button controls to increase/decrease the number of days for each event (i.e. add a new record where [DayNumber] is incremented by 1, and delete the last record if I have added too many day records).

I have added button controls to my EventDays subform and managed to use the macro builder to select and duplicate the last [DayNumber] record, but cannot figure out how to increase each successive [DayNumber] by 1.

1. Add a day...

Option Compare Database
Private Sub AddDay_Click()
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End Sub

2. Remove a day...

Option Compare Database
Private Sub RemoveLastDay_Click()
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End Sub