how to use field value in viewModelConfigDiff as comparison value in the other field in viewModelConfigDiff too

Hi,

I want to make a validator that endDate cannot be erlier than leave startDate, in endDate field in viewModelConfigDiff,

Expectation:

My Code:

"PDS_UsrLeaveEndDate_quo1xia": {
	"modelConfig": {
		"path": "PDS.UsrLeaveEndDate"
	},
	"validators": {
		"MySuperValidator2": {
			"type": "usr.FutureDateValidator2",
			"params": {
				"message": "#ResourceString(EndDateWarning)#",
				"startDate": "PDS_UsrLeaveStartDate_apq3vdm"
			}
		}
	}
}

   "usr.FutureDateValidator2": {
                validator: function (config) {
                    return function (control) {
                        let value = control.value;
                       let startDate =  config.startDate;
                        let valueIsCorrect = value > startDate;
                        var result;
                        if (valueIsCorrect) {
                            result = null;
                        } else {
                         console.log(startDate);
                         console.log(value);
                            result = {
                                "usr.FutureDateValidator2": { 
                                    message: config.message
                                }
                            };
                        }
                        return result;
                    };
                },
                params: [
                    {
                        name: "message"
                    },
                 {
                        name: "startDate"
                    }
                ],
                async: false
            },

But, value of startDate from the params is a String, how to get the actual value?

Thank you