Given two domains - Domain1 and Domain2- you want to create a trust relationship between Domain1 and Domain2 - that is, you want to add Domain2 as a trusted domain of Domain1.
Domain1 is the trusted domain of the domain where the sample script will run.
The user under whose context this script will run has administrative rights on Domain2.
Use the EstablishTrust method of IDomainTrustManagement to create the required trust relationship in one single operation.
Dim Trust As IDomainTrustManagement
'Get the interface.
Set Trust = GetObject ("NTDS://Domain1")
'Establish trust relationship with Domain2
Trust.EstablishTrust "Domain2", ONE_WAY_TRUST