Conditional format - Check for valid values

I have a query that return values from a table. These fields should
all be filled with data, but some are not, and some are filled with
wrong data. I need to have my users validate the data in this form. I
am currently using conditional format and using yellow background to
make the NULL values stand out. I'd like to have the fields with non-
valid data have red text.

I'm not sure how to write the expression for that in the conditional
format setup.

Here's the query the form is based on. I need to mark the [tag]!
[function_code] control with red text when it has a value that does
not exist in the [WM_GOC_Conversion]![Function_Code] field

SELECT Tag.Tag, Tag.Description, Tag.Tag_cat, Tag.Function_code,
Tag_diverse.Disiplin, Tag.System, Tag_diverse.Comm_Pkg, Tag.Area,
[Tag_format_in/_br/_te].Fire_area, Tag.Loop,
WM_GOC_Conversion.Function_code
FROM ([Tag_format_in/_br/_te] INNER JOIN (WM_GOC_Conversion RIGHT JOIN
Tag ON WM_GOC_Conversion.Function_code = Tag.Function_code) ON
[Tag_format_in/_br/_te].Tag = Tag.Tag) INNER JOIN Tag_diverse ON
Tag.Tag = Tag_diverse.Tag
WHERE (((WM_GOC_Conversion.Function_code) Is Null) AND ((Tag.Flag) Is
Null)) OR (((Tag.Loop) Is Null) AND ((Tag.Flag) Is Null)) OR
(((Tag.Description) Is Null) AND ((Tag.Flag) Is Null)) OR
(((Tag.Tag_cat) Is Null) AND ((Tag.Flag) Is Null)) OR
(((Tag.Function_code) Is Null) AND ((Tag.Flag) Is Null)) OR
(((Tag_diverse.Disiplin) Is Null) AND ((Tag.Flag) Is Null)) OR
(((Tag.System) Is Null) AND ((Tag.Flag) Is Null)) OR
(((Tag_diverse.Comm_Pkg) Is Null) AND ((Tag.Flag) Is Null)) OR
(((Tag.Area) Is Null) AND ((Tag.Flag) Is Null)) OR ((([Tag_format_in/
_br/_te].Fire_area) Is Null) AND ((Tag.Flag) Is Null));