>>TYPE("FiledName) <> "U" always worked for me. I don't remember any case where performence was a consideration.
>>I checked Fox 2.6 help and FIELD() function accepts only field # as first parameter and work area/alias as second.
>>
>This would fall if you have a variable name with the same name as your field name.

A field name in the current work area takes precedence over variable. In another work area you would prefix it with alias

TYPE("TableAlias.FiledName") <> "U"