Try moving the "AS Phone" part outside of the closing parenthesis. It looks like your IIf can be split up as:
IIF(
[Home Phone] IS NULL AND [H1 Cell Phone] IS NULL, -- Conditional
[Home Phone], -- Conditional true If they're both null, why are you displaying null here?
-- Conditional false
IIF(
[H1 Cell Phone] IS NOT NULL, -- Conditional
[H1 Cell Phone]&' (m)', - True
[Home Phone]&' (h)' - False
) AS Phone --I think the AS Phone part needs to be moved outside the IIF or removed entirely.
)
See http://office.microsoft.com/en-us/access-help/iif-function-HA001228853.aspx for examples on how to use IIF as well.