VBA to simulate poisson distribution

Hi again

I have entered the following function:

Public Function ranpoi(mean)
Dim Value As Double
Dim Prod As Double

Value = Exp(-mean)
Prod = 1

Do Until (Prod < Value)
ranpoi = ranpoi + 1
Prod = Prod * Rnd()

Loop
ranpoi = ranpoi - 1

End Function

And now I want to simulate x values from the possion distribution. So I've entered this code:

Sub PoiSimu2()
Dim lambda As Double
    
    lambda = Range("C2").Value
            
    With Range("T1:T1000")
        .Formula = "=randoi(Lamdda)"
        .Value = .Value
    End With

End Sub

But all cells returns #NAME? - why?

Hope that some of you can help me - maybe tell me, in short, what I'm missing about the syntax?