are you looking for Volume > than a Moving Average of Volume?

If(V>Mov(V,10,s),1,0)

or are you looking at todays volume is twice as much as yesterdays volume?

If(V>Ref(V,-1)*2,1,0);

You can create an indicator to plot on a chart {Indicator builder}

Greater Volume{Name}

MA:=If(V>Mov(V,10,s),1,0);

2V:=If(V>Ref(V,-1)*2,2,0);

MA;2V;

this will plot 1 if volume is greater than the 10 bar moving average of volume

it will plot 2 if the volume is twice as great as the previous volume

You can also use parts of the code in explorations as a filter or experts in the highlight section, it's up to you as to how to use this bit of code.

Now you want me to develop a system for you!

You can have the signals from an indicator{in a binary form} or you can show the signal with arrows using an expert or color the bar with a highlight from the expert.

You didn't mention if the signal comes from a standard length MACD or from a custom MACD, and if you wanted it to show a signal from the crossing above the signal line?

Did you want to use a trend filter, to only accept trades in long positions when the trend is rising?