Add a Plate Number(Fleet Management) in IW28/IW38

I need to add a Plate number(car License Plate no) in IW28 and Iw38 for easy search of fleet,in selection and output list.

since user knows only Plate number.

can any one suggest how would be added in IW28 and IW38.

I found user exit:IWOC0004 for this.

or is it any note available for the same.since it is standard field in SAP in IW21