Hi all,

I pass a range of cells to my function (the range is called "Atteso" ).
Inside the function I must recognize if its elements contain non numeric values to prevent strange
behaviour.
I tried the usufel IsNumeric but it seems that empty cells pass the IsNumeric test. I tried also
IsNull but the problem persists. Below I report the part of code:

If IsNumeric(Atteso(i)) Or Not IsNull(Atteso(i)) Then
tmp = prob_weibull(Atteso(i), Atteso(i - 1), ParA, ParB)
If tmp < 0 Then Ret_value = Ret_value + (osserv(i) - tmp) ^ 2 / tmp
End If

and relative called procedure if wanted

Function prob_weibull(x2, x1, ParA, ParB As Double) As Double
With Application.WorksheetFunction
prob_weibull = .weibull(x2, ParA, ParB, True) - .weibull(x1, ParA, ParB, True)
End With
End Function

Debugging the function step by step I noted that it crashes when the debug window reports to me no
values for Atteso(5) (nor numeric neither null string "" ). What does it mean? Is Atteso(5) null?
And why it passses the control "Not IsNull(Atteso(5))"?
Being more precise Atteso(5) refers to untouched cell (any kind of formulas inside)

Which controls I must do to allow crashes to my code?

I hope is all well explained.

Thanks for all suggestions, Alex.