Function Test(ByVal X As Double, ByVal T) As Double
Dim L As Long, X1 As Double, Y1 As Double, X2 As Double, Y2 As Double
If TypeName(T) = "Range" Then T = T.Value
L = WorksheetFunction.Match(X, WorksheetFunction.Index(T, 0, 1))
X1 = T(L, 1): Y1 = T(L, 2)
If L >= UBound(T) Then Test = Y1: Exit Function
X2 = T(L + 1, 1): Y2 = T(L + 1, 2)
Test = Y1 + (Y2 - Y1) * (X - X1) / (X2 - X1)
End Function