Avoiding duplicate long expressions in Excel

I often find myself writing Excel formulas that have something like this in the formula:

= IF(<long expression>=<some condition>,<long expression>,0)

Is there any way to accomplish this without needing to type out <long expression> twice (and also without using helper cells)?

Ideally, something that works similar to IFERROR, i.e.

= IFERROR(<some expression>,0)

This checks if <some expression> would return any type of error, and if it doesn't, it automatically returns <some expression> (without needing to again explicitly type it out a second time).

Is there an Excel function (or combination of Excel functions) similar to IFERROR but instead of checking an error condition, it checks a general (user-defined) condition based on the formula?