Customized LookUp dialogfield in Ax Report

public class ReportRun extends ObjectRun                                              //1st Method
{
   ItemId                    itemid;
   InventLocationId          inventlocationId;
   InventColorId             inventcolorId;
   InventSizeId              inventsizeId;
   Date                      mfdDate;
   str                       name;

   DialogField               dialogItemId;
   DialogField               dialogInventlocationId;
   DialogField               dialoginventcolorId;
   DialogField               dialoginventsizeId;
   DialogField               dialogMfdDate;

   InventTable               _inventTable2;

   #DEFINE.CurrentVersion(1)
    #LOCALMACRO.CurrentList
        itemId,
        inventlocationId,
        inventcolorId,
        inventsizeId,
        mfdDate
        #ENDMACRO

}

public Object dialog(Object _dialog)      // 2 nd Method
{
    DialogRunBase dialog = _dialog;
    ;

    dialogItemId            = dialog.addFieldValue(typeid(ItemId), itemId, 'Item Id');
    dialogInventLocationId  = dialog.addFieldValue(typeid(InventLocationId), inventlocationId, 'Factory');
    dialogInventColorId     = dialog.addFieldValue(typeid(InventColorId), inventcolorId, 'Color');
    dialogInventSizeId      = dialog.addFieldValue(typeid(InventSizeId), inventsizeId, 'Size');
    dialogMfdDate           = dialog.addFieldValue(typeid(Transdate), mfdDate, 'MFD date');

    return dialog;

}

public boolean getFromDialog()         //3rd method
{
    ;
    itemid           = dialogItemId.value();
    inventSizeid     = dialoginventSizeid.value();
    inventcolorid    = dialoginventcolorid.value();
    mfdDate          = dialogmfdDate.value();

    return true;
}

now i want to create a lookup suck type whenever someone  type a Item Id in dialog field box then the size and colour  list belongs to that item Id appears on ''size and colour dialog field ''