<div class='master'>
 <div class='recordBlock' id='gf5rtf4'/>
 <div id='d3dre'>First block</div>
 <div id='fa2s2w'>Second Block</div>
 <div class='recordBlock' id='fred11' />
 <div id='asd423'>Third block</div>
</div>

//div[@class='master']/div[not(@class = 'recordBlock')][ count(../div[@class='recordBlock'][3]/preceding-sibling::*) = count(preceding-sibling::div[@class='recordBlock'][1] /following-sibling::div[@class='recordBlock'][1]/preceding-sibling::*)]

//div[@class='master']/div[not(@class = 'recordBlock')][generate-id(../div[@class='recordBlock'][x])= generate-id(preceding-sibling::div[@class='recordBlock'][1]/following-sibling::div[@class='recordBlock'][1])]

//div[@class='master']/div[not(@class = 'recordBlock')][generate-id(../div[@class='recordBlock'][2]) = generate-id(preceding-sibling::div[@class='recordBlock'][1]/following-sibling::div[@class='recordBlock'][1])]

//div[@class='master']/div[not(@class = 'recordBlock')][generate-id(../div[@class='recordBlock'][3]) = generate-id(preceding-sibling::div[@class='recordBlock'][1]/following-sibling::div[@class='recordBlock'][1])]

//div[@class="recordBlock"]/following-sibling::div[not(@class)]