I wrote a custom function in VBA..

Function Test(Classe, osserv As Range, Dist As String, ParA As Double, ParB As Double) As Single
....
TMP AS double
....
Tmp = .Weibull(Classe(1), ParA, ParB, True) - .Weibull(0, ParA, ParB, True)
....
Tmp = .Distrib.Exp(Classe(1), ParA, True) - .Distrib.Exp(0, ParA, True)
....
Tmp = .Distrib.GAMMA(Classe(1), ParA, ParB, True) - .Distrib.GAMMA(0, ParA, ParB, True)

....

the first statement works fine.
The other two ones don't.

The parameters values are ParA=2 ParB=2 e Classe(1)=2

I included the three statements inside

"with Application.worksheet

....

end with".

May anybody help me, please? I can post the entire function.

Thanks Alex.