Excel VBA interpolate function

mInterpolate.bas

Public Function interpolate(knownValue As Double, knownRange As range, resultRange As range) As Double
    Application.Volatile
    Dim kR As Variant, uR As Variant, i As Integer, kBottom As Double, kTop As Double, uBottom As Double, uTop As Double, s As Integer
    kR = knownRange
    uR = resultRange
    If (Not UBound(kR) = UBound(uR)) Or UBound(uR) < 2 Then
        interpolate = CVErr(xlErrValue)
        Exit Function
    End If
    For i = LBound(kR) To UBound(kR)
        If knownValue <= kR(i, 1) Or i = UBound(kR) Then
            If i = LBound(kR) Then
                i = i + 1
            End If
            kBottom = kR(i - 1, 1)
            kTop = kR(i, 1)
            uBottom = uR(i - 1, 1)
            uTop = uR(i, 1)
            Exit For
        End If
    Next i
    interpolate = (knownValue - kBottom) / (kTop - kBottom) * (uTop - uBottom) + uBottom
End Function