If the quotes are entered in order, then what you want is to identify the most recent quote.
Do a Summary Maximum on the relationship to get the Maximum [Record ID#] up to the Client. call is [Record ID# of Most Recent Quote]
Look that up down to the Quote again and call it
Then do a new summary maximum of the Quote value subject to the filer that the [Record ID#] is equal to the value in the field [Record ID# of Most Recent Quote]
There will only be 1 record that matches so you will have that value up on the client record now.