Passing NULL parameters via TADOQuery


I am trying to pass null parameters to
an ADO TADOQuery but I'm getting exception?

I tried different solutions:
qrySQL.Parameters.Items[j].Attributes := qrySQL.Parameters.Items[j].Attributes + [paNullable];
qrySQL.Parameters.Items[j].Direction := pdInput;
qrySQL.Parameters.Items[j].Value := UnAssigned;

Also I tried to pass Null as value:
qrySQL.Parameters.Items[j].Value := Null;

The error what I get is everytime the same:
'Parameter object is improperly defined.
Inconsistent or incomplete information was provided'

The database what I use is SQL Server 6 in combi
with Delphi 5

What do i wrong ?

Any help is welcome.


Bernard Stibbe