you will have to show us how you use it, and what incorrect
results you get on what data.

If I have the following data: Cell A1 = -4, and cell B1 = ABS(A1) = 4.

In VBA, Range("B1").value = Abs(Range("A1").value) will give you the
same result.

Worksheetfunction.abs(expression) is not a supported function. For more
information, also type in abs  in the VBE search box, look at the Abs
function search result for possible errors.