Yes i have been looking at something similar also - I have used Edgeprox in the past but its the orderflow verison of the software and i ended up getting the ultimate version.
The only way I have done what you are asking for is "Theoratical Value" on the DOM - there is a white highlighted price where it shows you the theoratical breakeven after scaling in and out. It doesnt show it on the Chart window for some reason- its an easy fix for motivewave to do this but you know how that goes - here is a screenshot of what i'm talking about.
In this below example a 3 lot entry was taken so average entry is at the same level then a 1 lot profit was taken which pushed the THEO AVG (white) further below the Average entry- thats the only setting i've found to work to keep track of break even- you can set this up by using the PRICE COLUMN in the DOM SETTINGS window
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