This feature is added to VistaPro in VE 2013.
Summary (attached PDF has further detail if required):
1. With results loaded in VistaPro click the Visual Analysis (Model Viewer ll) button
2. With MV ll open click the MacroFlo Arrows (Model Viewer ll) button
3. Tick 'Enable MacroFlo Arrows feature' button (you can alter other settinsg here) and click Apply.