hi, 

see below code sample. I assume that you are familiar with  the DiamondManager web service. if this is not the case, I would take  a look here first http://technet.rapaport.com/Info/LotUpload/SampleCode/webService_Example.aspx.

code sample:

DiamondManager _manag = new DiamondManager();

_manag.Login("Username", "Password");

DeleteLotParameters dl = new DeleteLotParameters();

dl.ByField = ByFieldTypes.RapnetLotID;

dl.FieldValueList = "DiamondID_1,DiamondID_2.....,DiamondID_10";

_manag.DeleteLots(dl);