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https://www.mrexcel.com/forum/excel-questions/713005-does-point-fall-within-polygon-visual-basic-applications-function.html

Function PointInPolygon(rXY As Range, rpolyXY As Range) As Boolean
    ' Function checks if X,Y given in rXY falls within complex _
      polygon as defined by node list rpolyXY. _
      rXY to be 2 cell range with one X and one Y value _
      rpolyXY to be 2 column range with for each node on the polygon _
      the X and the Y point
    
    Dim i As Integer, j As Integer, polySides As Integer
    Dim oddNodes As Boolean
    Dim x As Double, y As Double
    Dim aXY As Variant
    
    oddNodes = False
    x = rXY.Cells.Value2(1, 1)
    y = rXY.Cells.Value2(1, 2)
    aXY = rpolyXY.Value
    
    polySides = rpolyXY.Rows.Count
    j = polySides - 1
    
    For i = 1 To polySides
        If (((aXY(i, 2) < y And aXY(j, 2) >= y) _
            Or (aXY(j, 2) < y And aXY(i, 2) >= y)) _
            And (aXY(i, 1) <= x Or aXY(j, 1) <= x)) Then
            oddNodes = oddNodes Xor (aXY(i, 1) + (y - aXY(i, 2)) / (aXY(j, 2) - aXY(i, 2)) * (aXY(j, 1) - aXY(i, 1)) < x)
        End If
        j = i
    Next i
    PointInPolygon = oddNodes
End Function