How do I actualise Currencies rate in Transfers between 2 banks accounts ?

Hi There, 

I have one quick question please ! 

Some of my clients are in France (pay in Euros) and I do have an USD bank account (Chase). 

I use a Transferwise account to receive those payments in Euros. Everything is set up well in QB.

A Client paid me in Euros in my Transferwise account on March 11. The Invoice is "PAID" in QB and is on my QB Transferwise register. Everything is fine.

QB automatically shows me on the invoice the conversion rate (€ to $) on that specific day (March 11).

But, I don't transfer immediately the funds from my Transferwise account (Euros) to my Chase account (USD), I usually wait few weeks (looking for a better exchange rate, which is not always possible).

How do I say to QB when I will transfer from Transferwise (€) to Chase ($) that there is an other exchange rate ?

Example :

In my QB Invoice PAID on March 11:

795 € = $885 

But now I need to transfer from Transferwise (€) to Chase ($) but the exchange rate is not that good : today,

795€ = $ 858.

How do I do so that the difference will be "aknowledge" but QB and regarding as an expense (or a lost) ?

I hope my question is clear. Thanks for your help.

Greg