You'd need to create an IEdmFile6 instance. In the EmdCmd_PostAdd hook, you're given the ID of the file in the mlObject2 member of the EdmCmdData struct.
Dim file as IEdmFile6 Dim vault As IEdmVault11 = TryCast(poCmd.mpoVault, IEdmVault5) For Each data As EdmCmdData In ppoData file = vault.GetObject(EdmObjectType.EdmObject_File, data.mlObjectID2) file.RenameEx(poCmd.mlParentWnd, "New Name", 0) Next
This is untested and I don't use VB, but it should point you in the general direction. HTH!