Utilisation non autorisée de NULL

Bonjour
C'est une erreur Visual Basic dont voici des explications venant de l'aide de VB

Null is a Variant subtype used to indicate that a data item contains no valid data. This error has the following cause and solution:

· You are trying to obtain the value of a Variant variable or an expression that is Null. For example:

MyVar = Null
For Count = 1 To MyVar
. . .
Next Count

Make sure the variable contains a valid value.

For additional information, select the item in question and press F1.