Hello Christian, how are you ?
In that case

x=100
activex.method(x)

the error is not trigger, but... Doesn't work too. :O)

I' tried a new think :

Set udfparms to REFERENCE
x=100
activex.method(x)

The error occurs..

The type of parameter in type library information is VT_PTR.

May be it's help us . or not.. :O)

Bye, thanks for your help.