How customize query by current branch in processing create order requisition screen

How can we apply dynamic query in processing requisition create order screen ?

I try this but cannot solve

public class RQRequisitionProcess_Extension : PXGraphExtension<PX.Objects.RQ.RQRequisitionProcess>
{
    public virtual IEnumerable records()
    {
        foreach (var item in this.Base.Records.Select())
        {
            RQRequisition rQRequisition = (RQRequisition)item;
            if(rQRequisition.BranchID == PXContext.GetBranchID()) 
            { 
                yield return item;
            }
        }
    }
}