To restrict MA modification once CD is in Executed phase

Hi Experts,

We are in sourcing 10.0.

We have one business requirement to restrict users to modify any data of MA once the contract document is in Executed state.

I have written code but it's throwing an error before moving the phase to Exceuted phase,

KDOCcollection = doc.getContractDocuments();

if (KDOCcollection.size() != 0)

{

iter = KDOCcollection.iterator();

while (iter.hasNext()) {

oldKDOC = iter.next();

if (KDOCcollection.size() == 1){

  if(oldKDOC.getCurrentPhase().getDisplayName(session).equals("Executed")){

  throw new ApplicationException("Doucment is in Executed state, you cant amend contract");

}

}}

}

Any leads would be of great help!!

Regards,

Geetika