Hundreds of checkboxes change from True/False to Yes/No

I have a spreadsheet that is continuously being updated to track visitations to patients. I have 2 columns that I've used the below VBA code to enter multiple checkboxes into which are assigned to the cell into which they are located. However, I would like to add something that makes the value of the checkboxes either Yes or No when I click on them. There are over 600 of these in the spreadsheet, so I need something that will cover all of them at once instead of having to change each one separately. I would post a pic of the spreadsheet, but I can't yet since I'm a new user and don't have reputation points. Can anyone help?

Sub AddCheckBoxes()

Dim cb As CheckBox
Dim myRange As Range, cel As Range
Dim wks As Worksheet

Set wks = Sheets("Sheet1")

Set myRange = wks.Range("K2:K300, L2:L300")

For Each cel In myRange

Set cb = wks.CheckBoxes.Add(cel.Left, cel.Top, 30, 6)


With cb

    .Caption = ""
    .LinkedCell = cel.Address

End With

Next

End Sub

End Sub