Tests the value of an expression to determine whether it is NULL.
IsNull ( expr )
expr
Any expression except an object reference or a Variant that contains an object reference.
The IsNull function returns TRUE (-1) if expr is NULL; otherwise it returns FALSE (0).
The IsNull function checks whether a Variant contains NULL. For example:
If IsNull(LoVar) Then Print "LoVar is NULL" Else Print LoVar
Do not use the IsNull function with an object reference variable argument; to test whether an object reference variable has been initialized, use (objref Is Nothing).
Built-in constants in LotusScript language
Testing object references in LotusScript language