#Error, Nz, Div!/0 and other situations

[Greg Green]

Following on yesterday's post and answers about the Nz function, I have a
similar problem.

When all fields have data, this returns no result:
=([D18]*[D27])/(Nz([A18]-[B18]-[C18]),1)

This returns a result if denominator > 0:
=([D18]*[D27])/(Nz([A18]-[B18]-[C18]))

Even with:
=([D18]*[D27])/(Nz([A18]-[B18]-[C18]),1)
The denomiator can be zero, since Nz converts Null to zero but leaves zero
alone.

I tried the IIF function, but it seems to prefer text