>>>>>>Is it possible to create an index tag on a field that would enforce unique entry in the field, unless the entry is blank (no entry)?
>>>>>
>>>>>You can have a candidate index On myfield with NOT EMPTY(myfield) in For clause.
>>>>
>>>>Thank you very much. By the way, I did try it before I posted the question but I missed entering the field name in the EMPTY() expression.
>>>
>>>You welcome. Make sure you don't have NULL values in the field.
>>
>>I won't have NULL values but what got me a little concerned is what Borislav said about optimization. I am thinking that maybe I should have another index tag on this field, just for optimizing queries. Does it make sense?
>
>Rushmore doesn't use indexes with For clause.

Not 100% correct according to http://www.code-magazine.com/article.aspx?quickid=0404022&page=3 This has to be re-checked carefully and I was searching information in the meantime, but now have to stop my search due to some pressing problems....