How to add New XMLport Node to our existing XMLport,dynamically?

Hey experts,
Here i need a solution from u guyz.
I have a XML port to import XML file,but problem is here that..XML file which i m gonna to import have some nodes/element that have values on condition base..
eg.<CAD_DETAILS>
<CAD>
<Account>G0183</Account>
<CustomerName>GO INTERNATIONAL</CustomerName>
<invoice_number>
</invoice_number>
<Invoice_Date>
</Invoice_Date>
<Due_Date>
</Due_Date>
<ShipmentDate>01/22/2017</ShipmentDate>
<ShipmentNumber>XJ560665148JF</ShipmentNumber>
<AccountManager>Warren Lee</AccountManager>
<customerref>37560018277</customerref>
<MAWB>16039539080</MAWB>
<Service>ADC</Service>
<Origin>HKG</Origin>
<Dest>ITA</Dest>
<ShipperName>Go International Limited</ShipperName>
<ConsignorAddress>
</ConsignorAddress>
<ConsigneeName>filippo fenili</ConsigneeName>
<ConsigneeTel>35214270</ConsigneeTel>
<ConsigneeAddress>
</ConsigneeAddress>
<receiverZip>24128</receiverZip>
<destName>Italy</destName>
<DestCountry>Italy</DestCountry>
<SentTo>
</SentTo>
<Flight>
</Flight>
<Coloader>DPDCDG</Coloader>
<AlternateNumber>5000953700</AlternateNumber>
<AWB_Counts>1</AWB_Counts>
<Pieces>1</Pieces>
<Pack_Type>N</Pack_Type>
<Weigt>0.480</Weigt>
<VolWeight>0.480</VolWeight>
<ChargeableWeight>0.480</ChargeableWeight>
<Weight_Charge>0.480</Weight_Charge>
<ServiceAmount>96.00</ServiceAmount>
<spotRate>N</spotRate>
<First_0.5>N</First_0.5>
<AAA>N</AAA>
<AAC>Y</AAC>
<AAC_Amount>52</AAC_Amount>
<ADC>Y</ADC>
<ADC_Amount>96.00</ADC_Amount>
<ADCI>N</ADCI>
<ADF>N</ADF>
<ADO>N</ADO>
<AF>N</AF>
</CAD>
</CAD_DETAILS>

in this xml file if AAC have value 'Y',only then the next element will be there AAC_Amount in xml file otherwise not.
How can i handle this kind of situation,becuz if i need to read all XXX_Amount element in my XMLport.