InfoPath Dev

I have a field called ValuePerUnit which has a default value of TotalLand/TotalUnits.  Total Land and Total Units are derived by respective sums of rows in a repeating table.  When I first open the form, the ValuePerUnit field displays NaN in it.  I know this is for Not a Number but what can I do so this doesn't display?  It goes away as soon as data is entered in the a Unit field.

Thanks! 

How about hiding the ValuePerUnit field on the condition ValuePerUnit = "NaN"?

 Another option would be to use the default value formula TotalLand / (TotalUnits + (TotalUnits = 0)) which should result in a value of 0 if TotalLand and TotalUnits are both 0.

The default formula wouldn't work - InfoPath didn't like the syntax so I went with hiding the field.  Thanks for your help.