James, not sure how to achieve the shading but here's something that may form a basis for further ideas. This will plot a line that will be horizontal (at 50.6Hz) except where the tag excedds 50.6Hz.
Create a dataset using the following Expression:
Code:(('tag'<=50.6)*50.6)+(('tag'>50.6)*'tag')
Set the Interval to something suitable - for Frequency over 1 hour you could possibly use 1s (one second).
Choose Value from "Columns:",
place this dataset in your Trend and move it to the top of the list.
MilesUK
ProcessBook v3.0.15.3
