can you develop a scan for stocks selling below book value? If so, can you set parameters?

There isn't a way to include Book Value in a Personal Criteria Formula, but you can plot Current Book Value Per Share in the same pane and scale as price. This would allow you to click on price and select Create Scan Condition to create a condition for price being below book value.

You could also plot Price to Book on the chart and click on it to select Create Scan Condition to create a condition for Price to Book being less than 1. This will be true if and only if price is below book value.

Create Conditions from Your Chart (5:25)
Building a Scan with Multiple Conditions (7:29)