Crystal Reports Adding with null values

Message

     I'm trying to add field values together to get a total in another field.  The problem is that one of the fields may have null value in it.  When it does, Crystal does not want to add any of the other fields and returns a blank.  What syntax do I use to make Crystal add all the fields regardless if one of them is null?

Normally, in MS Access I would use nz.  But obviously doesn't work with Crystal.

Thanks for any help in advance.

Using Crystal 8.5