Another method
There is another method to analyze the length of a contour from a sketch. This will involve creating a Parameter and assigning a formula
1) Select the f(x) icon
2) Create a length Parameter
3) Add a formula to this parameter
4) In the Dictionary pane select Measures
5) In the Members of Measures double click Length (Curve,...): Length - this will place the operation length() in the formula definition field
6) The cursor should be between the parenthesis () now double click on the sketch contour - the formula should look something like this: length(PartBody\Sketch.1)
7) Select the OK button
8) Select Yes for Auto Update
9) Select OK
This will create a parameter that will report the total length of the Sketch. If the sketch changes the parameter is updated to reflect the new length.