Can someone help with this Martlett code?

Can someone help with this Martlett code?

In Excel, this code works, but in Zoho, nothing happens when cells A3 through A100 is clicked.
  1. Private Sub Worksheet_SelectionChange(ByVal Target As Range)
  2.     If Target.Cells.Count > 1 Then Exit Sub
  3.         If Not Intersect(Target, Range("A3:A100")) Is Nothing Then
  4.             Target.Font.Name = "Marlett"
  5.                 If Target = vbNullString Then
  6.                     Target = "a"
  7.                 Else
  8.                     Target = vbNullString
  9.                 End If
  10.         End If
  11. End Sub
What it should do (and does in Excel) is put an "a" in the cell (column a) when it's selected, and the font should be Martlett so that it appears to be a checkmark.  By doing so, I will be able to sort the spreadsheet so that checked rows will be dropped to the bottom of the list.

Here's what the spreadsheet looks like (in Excel with cells A4 & A6 clicked on)...


The spreadsheet is exactly the same in Zoho.  But the code doesn't do anything.  Is there an adjustment needed to be made in Zoho to get it to work?

To explain what I'm trying to do...I want this to be a shared file that users can choose a business that they plan to hire by selecting it by clicking in column A.  Once that's done, I will write a sorting code that will move any selected rows (based on column a's cells holding "a" = Martlett font check mark) to the bottom of the list so that the next user will open the file, and choose their vendors from the top of the list down. (Ensuring that a business that was recently selected would be less likely to be chosen again before those above it.)

I'm also willing to accept other solutions that will accomplish the same scenario I explained above. 

Thanks in advance!