Trade from chart drawings

First time poster... so hello all.

I can not seem to find an answer to this through googling and searching NexusFi (formerly BMT) forums, just seems like it should be easy though.

Does anyone know a charting software that will allow you to trade on sloped lines? So if you just had a basic channel for instance, you could enter a limit buy order on the lower channel, where the price would change as it moved through time (or ticks, whatever your bars are based on).

I use Sierra currently, they said it's not supported when I asked on their support board.

Thanks in advance, and thank you Mike for the great site.