Dear Ludwing ,
Thanks for your response I have manage it now through vendtable and dirpartytable relation in lookup method which have both vendor account and name and I am adding it through code
public void lookup()
{
Query query = new Query();
QueryBuildDataSource qbds;
QueryBuildDataSource qbdsJoin;
SysTableLookup sysTableLookup = sysTableLookup::newParameters( tableNum(VendTable), this);
;
if(BankAccountTrans.Included==NoYes::Yes)
{
qbds= query.addDataSource( tableNum(VendTable));
qbdsJoin= qbds.addDataSource( tableNum(DirPartyTable));
qbdsJoin.relations( false);
qbdsJoin.fields().dynamic(NoYes::Yes);
qbdsJoin.addLink( fieldNum(VendTable, Party), fieldNum(DirPartyTable, RecId));
qbdsJoin.joinMode(JoinMode::InnerJoin);
sysTableLookup.parmQuery(query);
sysTableLookup.addLookupfield( fieldNum(VendTable, AccountNum), true);
sysTableLookup.addLookupfield( fieldNum(VendTable, Party));
sysTableLookup.performFormLookup();
}
}