In Standard form Bring New number Seq with Customized Field without clicking any button

PurchParmTable -- table -- created new number seq method

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client server static NumberSequenceReference numLEC_ProductNumber()
{
     return NumberSeqReference::findReference(extendedTypeNum(LEC_ProductNumber));
}
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PurchEditLines -- Form -- Created one new method

public void generateLECGRNNumber(ParmId  _parmId)// added by kavin on march 29th 2019 for bring number seq in form PurchEditLines field name LEC_GRnumber
{
    PurchParmTable      _PurchParmTable;
    NumberSeq           numberSeq;
    LEC_ProductNumber   num;

    select forUpdate _PurchParmTable
        where _PurchParmTable.ParmId == _parmId;

    if(_PurchParmTable)
    {
        numberSeq = NumberSeq::newGetNum(PurchParmTable::numLEC_ProductNumber());
        num = numberSeq.num();

        ttsBegin;
        _PurchParmTable.LEC_GRN = num;
        _PurchParmTable.update();
        ttsCommit;
    }

}

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receiving argument from init ()

  element.generateLECGRNNumber(parmId); // added by kavin for bring parmid to get recid for table on march 29th 2019