DAS Hotkey to scale in a position (NOT Free Roll)

[Hamish Arnold 1]

Does anyone have 2 hotkeys (long and short) to facilitate a scale into a position?

For example, if going long and the price action is looking interesting for an entry at, say $50, and you want to take a long with a stop at $49 and a risk level of $100, then would purchase 100 shares.  Then you want to add to the position, but keep your risk at a maximum loss of $100 but you are happy to reduce the stop loss level up to $49.75, but can still but into the position at $50 (to keep the example easy!), the you should ultimately have a position of 400 shares - so the click on the chart would be at $49.75 and the hotkey would result in a purchase of an additional 300 shares.  This would be like a free roll, but where you are still accepting a degree of downside risk, rather than only using the unrealized P&L to determine the additional shares...

All ideas welcome!