If you want it to look exactly like the numeric limit test, that is going to be a bit trickier. You could use the additional results settings for the step to log the limits and value, however they will not show up in the table the same way that they do for numeric limit test steps. If that's not acceptable, then another thing you could do is make your own private copy of the NumericLimitTest step type and call it something like MyCompanyName_NumericLimitTestUI64. Then, in your new step type, change the representation of Result.Numeric, Limits.Low, and Limits.High to UI64. Whenever, you select the step though you will get an error dialog because the edit pane for the limits does not know how to handle UI64 representation, but it seems to be harmless to just press OK on the error dialog. You however cannot specify the step with the limits pane, you instead have to specify it in the variables view by setting Step.Limits.LowExpr, Step.Limits.UseLowExpr, Step.Limits.HighExpr, and Step.Limits.UseHighExpr. I verified that it does seem to execute ok if you do this. I'm not sure if there are any other problems with this, so you might want to test around it a bit to make sure it works well enough for your purposes.
Hope this helps,
-Doug
