5% calculation in Oanda

Hi.
I'm trying to have an Excel formula to tell me how many units must I trade so if I loose I loose 5% of my account. I'm using Oanda so there's the "UNITS" thing.
Let's say I have $1000 and I know that in a trade my SL is 25 pips. How many units should I trade so if I loose 25 pips I'll loose 5% of my account?
Thanks in advance.

If you go to Tools/User Preference/Trading you'll find a box where you can set your default stoploss to a percentage of your account balance. Then it'll set your stop to whatever percentage you choose, unless you change it manually.

At the top of the box, you can set which pair(s) to apply the default to.

$1000 * .05 = $50

$50/25 pips = $2 pips

Set your units to whatever it needs to be to have $2 pips. You can see the pip value in the order window for whatever amount of units you enter.