Option Explicit
Function MapTab(ByVal X#, ByVal Y#, ByVal Rng As Range) As Double
Dim L&, C&
L = WorksheetFunction.Match(Y, Rng.Columns(1))
C = WorksheetFunction.Match(X, Rng.Rows(1))
MapTab = Intpo2D(X, Y, Rng(1, C).Value, Rng(L, 1).Value, Rng(1, C + 1).Value, Rng(L + 1, 1).Value, _
Rng(L, C).Value, Rng(L, C + 1).Value, Rng(L + 1, C).Value, Rng(L + 1, C + 1).Value)
End Function
Function Intpo2D#(ByVal X#, ByVal Y#, _
ByVal X0#, ByVal Y0#, ByVal X1#, ByVal Y1#, _
ByVal Vx0y0#, ByVal Vx1y0#, ByVal Vx0y1#, ByVal Vx1y1#)
X = (X - X0) / (X1 - X0)
Y = (Y - Y0) / (Y1 - Y0)
Intpo2D = Vx0y0 + X * (Vx1y0 - Vx0y0) + Y * (Vx0y1 - Vx0y0) + X * Y * (Vx0y0 - Vx1y0 - Vx0y1 + Vx1y1)
End Function