How to shorten if statements that refer to full formula

Found the code eventually,

Public Function V(Optional vrnt As Variant) As Variant
'
' Stephen Dunn
' 2002-09-12
'
Static vrntV As Variant
If Not IsMissing(vrnt) Then vrntV = vrnt
V = vrntV
End Function

=IF(ABS(V(SUMPRODUCT(....)))<1,0,V())

Probably the easiest way to shorten repeated chunks of formula without extra cells or defined names.