Plotting horizontal line on a graph

["antmar65" <antmar65@xxxx>]

Hi,
I am a new user of Amibroker
I want to plot one horizontal line on a graph.
I try to do it with this formula (to plot a red line that is 
referring to precedent bar's High):

Plot(LastValue(Ref(H,-1)),"H",32,1)

This formula would have to design one horizontal red line, but this 
formula don't plot an overlaying line: it only adds a line under the 
graph.
How can I do?

Ant