All of our <a href='http://www.hishairclinic.com/category/case-studies/' target='_blank' rel='nofollow'>past customers</a> agree that the only way someone would know they <b>have had</b> treatment would be if they had chosen to tell them.<br/><br/>And<br/><br/>All of our agree that the only way someone would know they <b>had had</b> treatment would be if they had chosen to tell them.<br/><br/>Which sentence is correct and how is the past perfect tense used here when it's not describing a situation of another past event?<br/><br/>Thanks.