Why Create an XLL-Based Worksheet Function

Why Create an XLL-Based Worksheet Function

An XLL is a Windows DLL that is structured so Excel can recognize and open it directly. Because worksheet functions built into XLLs are compiled to machine code and treated by Excel as if they were native worksheet functions, they are extremely fast. You can create custom versions of worksheet functions that Excel doesn't get quite right as well as creating worksheet functions that Excel doesn't provide at all.

Also, Excel doesn't store hard-coded paths to XLL-based worksheet functions, so they don't suffer from broken links when files are relocated like VBA add-in based functions do.