Stocks, advanced portfolio and multi-currency

[Stefano M Canta]

Hello,
I have the following problem.
I am based in the US and my company offers a share purchase plan.
I invested 12766.46 USD to buy 181.223261 shares of MDA.TO, which is
exchanged in Toronto. The brokerage valued 12766.46 USD to be 13133.55 CAD
on May 8th 2013.

The overall transaction is 12766.46 USD -> 13133.55 CAD -> 181.223261 MDA.TO
.

Now I want to use the advanced portfolio report to to show my basis, and
the possible gain, in USD.

The problem is that the report uses the 13133.55 CAD but converts this
value to USD using the online quote instead of the original price of
12766.46 USD. So every day my basis changes... This is not the behavior
that I want to see for the basis. I am fine with the value of the stock
changing every day according to the market value of MDA.TO and the
conversion rate of USD to CAD, but the basis should only be related to the
day I bought the stock.

How do I change that in the report?

Thanks,
Stefano