I am trying some conditional formatting and cannot get it to work quite right

I am using conditional formatting to try to get different coloured text.

I have a field in a matrix that is a date - if it is less than today then it should be red, if it is between 1 and 35 days in the future it should be orange and if it is outside that it should be green.

I am using the following and all I am getting is red and green, the orange doesn't seem to work as i have probably got the datediff things wrong.

=IIf(Max(Fields!AchievementRecordExpiryDate.Value) < Now(),"Red", IIf(datediff(dateinterval.Day,
Max(Fields!AchievementRecordExpiryDate.Value),NOW()) < 35 And datediff(dateinterval.Day,
Max(Fields!AchievementRecordExpiryDate.Value),NOW()) >= 0, "Orange","Green"))

Any help would be really appreciated

Thanks

Rich