pass by ref in VB .net

I have a managed c++ dll with function
void getPkts(int *totalPkts);
in which totalPkts will be returned as an out parameter(means it pass
by ref).
BTW, getPkts is member function of class client.
Now, from VB .Net, I do
Private client1 As Client = New Client
Dim pktCnt As Integer = 0
client1.getPkts(pktCnt%)

The following error message is displayed when I build this VB project
"getPkts has a return type that is not supported or parameter types
that are not supported.

Any idea?