A colleague has found the following Excel function online
Public Function PtInPoly(Xcoord As Double, Ycoord As Double, Polygon As Variant) As Variant
Dim x As Double, m As Double, b As Double, Poly As Variant
Dim LB1 As Double, LB2 As Double, UB1 As Double, UB2 As Double, NumSidesCrossed As...