Error with pivot items in pivot table

Let's say I have a Pivot Table that looks like this but it has over 50 rows:

Letter	Hours
A	5
C	10
D	8

In the table above the Letter B has a total of 0 hours so it is filtered out; therefore, it isn't displayed.

I want to create a loop that displays the number of Hours for each Letter that is in the table. When it gets to Letter B, I get an error. What's the workaround?
Here's my code:

For Each pt_item In pt.PivotFields("Letter").PivotItems     
     MsgBox pt.PivotFields("Letter").PivotItems(pt_item.Value).DataRange.Value
Next

Thanks!