How to filter lookup data based on column value (State/Region) in multi-select dropdown

Hi Community,

I’m working on a requirement where I need to filter Region lookup data in a multi‑select dropdown field based on a column value (State/Region).

Basically, when a user opens the lookup field, it should only display the records that match the given State condition.

Here is my viewConfigDiff code:

viewConfigDiff: /**SCHEMA_VIEW_CONFIG_DIFF*/[
...
{
				"operation": "insert",
				"name": "MultiSelect_ugo4wdi",
				"values": {
					"layoutConfig": {
						"column": 1,
						"row": 3,
						"colSpan": 2,
						"rowSpan": 1
					},
					"type": "crt.MultiSelect",
					"label": "#ResourceString(MultiSelect_ugo4wdi_label)#",
					"recordId": "$Id",
					"recordRelationColumnName": "ImpAccount",
					"selectSchemaName": "ImpStateInterestMultiselect",
					"selectColumnName": "ImpStateInterestField",
					                          "selectFilter": {
      "items": {
        "filterByRegion": {
          "comparisonType": 3,
          "isEnabled": true,
          "filterType": 1,
          "leftExpression": {
            "expressionType": 0,
            "columnPath": "ImpStateRegion"
          },
          "rightExpression": {
            "expressionType": 2,
            "parameter": {
              "dataValueType": 1,
              "value": "State"
            }
          }
        }
      }
    },
					"visible": true,
					"labelPosition": "above",
					"placeholder": "",
					"tooltip": ""
				},
				"parentName": "GridContainer_qy480gv",
				"propertyName": "items",
				"index": 3
			},
			...
			]/**SCHEMA_VIEW_CONFIG_DIFF*/,

I’ve tried adding filtering logic in the source code, but I’m not getting the expected result. Here is my handler code:

handlers: /**SCHEMA_HANDLERS*/[
			{
  request: "crt.LoadDataRequest",
  handler: async (request, next) => {
    // Ensure this runs only for your MultiSelect list data source
	    console.log("Current DataSourceName:", request.dataSourceName);
	   console.log("EntitySchema:", request.entitySchemaName);
 
    // Ensure it's the right source + schema
 
    if (request.dataSourceName !== "MultiSelect_ugo4wdi_List_DS") {
		console.log("Hello I am in a log box 1234");
      return await next?.handle(request);
    }
 
    const filter = new sdk.FilterGroup();
 
    // Filter where ImpStateRegion == 'State'
    await filter.addSchemaColumnFilterWithParameter(
      sdk.ComparisonType.Equal,
      "ImpStateRegion", // <-- Column in ImpStateInterestMultiselect to filter on
      "State"           // <-- The fixed value to filter by
    );
 
    // Workaround for Creatio DevKit filter bug
    const newFilter = Object.assign({}, filter);
	  console.log("Hello I am in a log box");
    newFilter.items = filter.items;
 
    // Add filter to request parameters
    request.parameters.push({
      type: "filter",
      value: newFilter
    });
 
    // Proceed with next handler
    return await next?.handle(request);
  }
}
 
		]/**SCHEMA_HANDLERS*/,

I’ve also attached a screenshot of the current setup.

Can someone guide me on how to correctly apply filters for a multi‑select lookup field?
Do I need to configure this through the business rules, or is filtering only possible via overriding the source code handler?

Any help or examples would be greatly appreciated!

Thanks in advance.