Function to count if cell each cell in horizontal range is max for it's respective column

You are using MAX property incorrectly. The code you are using would check only 2 cells. This is how it should be used-

Function CountIfMax(Myrange As Range, n As Integer) As Double

Dim i As Integer
Dim cell As Range

i = ActiveCell.Row

For Each cell In Myrange

    Max = Application.Max(Range(Cells(i - n, cell.Column), Cells(i + n, cell.Column)))
    actcell = Cells(i, cell.Column)

    If actcell = Max Then
        CountIfMax = CountIfMax + 1
    End If

    
Next cell

End Function