How make a field uneditable/readonly on click of a button

Summary: We have a required where if party data is published through button, relationship data should be uneditable or make it readonly on click.

Content (required): Account Relationships.

Version (include the version you are using, if applicable): 23D

Code Snippet (add any code snippets that support your topic, if applicable): Added code on AfterTransactionPosted, but not working.

if(PublishRemarks_c == 'Published to Registry')

{

def accCollection = Accounts_Accounts_CO_Rel_Tgt;

while(accCollection.hasNext())

{

 def accCollectionRow = accCollection.next();

 def accRelCollection = accCollectionRow?.AccountRelationshipsCollection_c

 while(accRelCollection.hasNext())

 {

  def accRelCollectionRow = accRelCollection.next();

  if(accRelCollectionRow.RelationEndDate_c != null)

  {

   return false;

  }

  if(accRelCollectionRow.RelationType_c != null)