Option Explicit
Function IntpoLinTbXY(ByVal X As Double, ByVal RgXY As Range) As Double
Dim L As Long, TXY()
L = WorksheetFunction.Match(X, RgXY.Columns(1))
TXY = RgXY(L, 1).Resize(2, 2).Value
IntpoLinTbXY = IntpoLin(X, TXY(1, 1), TXY(1, 2), TXY(2, 1), TXY(2, 2))
End Function
Function IntpoLin(ByVal X As Double, ByVal X1 As Double, ByVal Y1 As Double, _
ByVal X2 As Double, ByVal Y2 As Double) As Double
IntpoLin = Y1 + (Y2 - Y1) * (X - X1) / (X2 - X1)
End Function