Removes a Location named "B_INV" from the list of locations based on a selected warehouse (SiteID)

TESTPKG.CODE.cs

using System;
using PX.Data;
using PX.Data.BQL;
using PX.Objects.IN;

namespace TEST
{
    public class LocationExtType
    {
        public const string B_INV = "B-INV";
        public class b_INV : PX.Data.BQL.BqlString.Constant<b_INV>
        {
            public b_INV() : base(B_INV) { }
        }
    }
    public class LocationExtAttribute : LocationAttribute
    {
        public LocationExtAttribute(Type SiteIDType, Type ExcludeLoc) : base(SiteIDType)
        {
            _SiteIDType = SiteIDType ?? throw new PXArgumentException(nameof(SiteIDType), ErrorMessages.ArgumentNullException);

            Type search = BqlTemplate.OfCommand<
                    Search<INLocation.locationID,
                    Where<INLocation.siteID, Equal<Optional<BqlPlaceholder.A>>,
                    And<INLocation.locationCD, NotEqual<BqlPlaceholder.B>>>>>
                .Replace<BqlPlaceholder.A>(_SiteIDType)
                .Replace<BqlPlaceholder.B>(ExcludeLoc)
                .ToType();

            var attr = new LocationDimensionSelectorAttribute(search, GetSiteIDKeyRelation(SiteIDType));
            _Attributes.Add(attr);
            _SelAttrIndex = _Attributes.Count - 1;
        }
    }

    public class InventorySummaryEnq_Extension : PXGraphExtension<PX.Objects.IN.InventorySummaryEnq>
    {
        public static bool IsActive() => true; // Check for Feature

        [PXMergeAttributes(Method = MergeMethod.Replace)]
        [LocationExt(typeof(InventorySummaryEnqFilter.siteID), typeof(LocationExtType.b_INV), Visibility = PXUIVisibility.Visible, KeepEntry = false, DescriptionField = typeof(INLocation.descr), DisplayName = "Location")]
        protected void _(Events.CacheAttached<InventorySummaryEnqFilter.locationID> e) { }
    }
}

TESTPKG.CODE.Simple.cs

using System;
using PX.Data;
using PX.Data.BQL;
using PX.Objects.IN;

namespace TEST
{
    public class LocationExtType
    {
        public const string B_INV = "B-INV";
        public class b_INV : PX.Data.BQL.BqlString.Constant<b_INV>
        {
            public b_INV() : base(B_INV) { }
        }
    }
    
    public class InventorySummaryEnq_Extension : PXGraphExtension<PX.Objects.IN.InventorySummaryEnq>
    {
        public static bool IsActive() => true; // Check for Feature

        [PXMergeAttributes(Method = MergeMethod.Append)]
        [PXRestrictor(typeof(Where<INLocation.locationCD, NotEqual<LocationExtType.b_INV>>),"")]
        protected void _(Events.CacheAttached<InventorySummaryEnqFilter.locationID> e) { }
    }
}

Simple version added after good note by Daryl Bowman