Mixing Text & Length Parameters in a Formula

[msinclair.138873]

I'm attempting to create a ceiling schedule that will pull the ceiling height from the ceiling objects. There are cases, however, where we would like to override that height with a text string such as "varies" or "structure".
Currently, I an trying to do this override through a formula parameter which uses an If statement...if the ceiling height is 0'0", then the text parametr will be schedules...otherwise the true ceiling height is scheduled.
I keep getting inconsistant unit warnings when using text and length parameters in the same formula. Should I be dividing the length by something to cancel the units? LF?

Thanks-