How do I determine if a range exists, with the Excel 97 SDK [Excel4()]?

Question

I need to know if a range exists, in my Excel addin. I use the Excel97 SDK (the Excel4() function).

For instance, I have a range named:

NotARealSheet!R1X10

When I set it to an XLOPER, it sets correctly, but when I use it, I get an untrappable error. At least, I can't figure out how to trap it.

I would like to know, before I use the XLOPER, if the range is correct.