Hello,
If want a field to appear in the test lab execution grid view, the UDF would have to be added to the Test Instance User Fields area as a UDF there.
Adding a UDF to the Test Set > User Fields would only have this UDF present in the Test Set details only and that is not what the execution grid columns under Test Lab show.
See below pics to illustrate what I mean.
If I am incorrect in what you are wanting, please let me know.
![alt text][1]
And here is the execution grid view, where I used the Select Columns menu button to add the UDF ''My Order'' to the view.
![alt text][2]
[1]: /storage/temp/524-test-instance-field.png
[2]: /storage/temp/526-execution-grid-view-with-udf.png