Change Text Color of date if expired (datediff)?

[roattw]

I have looked at the posts on this topic using a Yes/No field.  But would be possible to do it with  DATEDIFF?  

I have two simple fields.  A submit_date (timestamp)  and a deadline_date (text field as calendar popup).  The app requires a minimum of 30 days to complete a request.  So if someone submits a request (submit_date) and chooses a deadline date (Deadline)  that does not meet then 30 day minimum notice we need that Deadline date text to be read preferrably  (or the field background, or row).  Ive tried versions of this:
 

<div =id="visi [@field:Deadline]">

<script>
var isi = document.getElementById("visi[@field:Deadline]");
if DATEDIFF(day, [@field:Sub_date], [@field:Deadline]) <= 29 {
isi.parentNode.parentNode.style.backgroundColor = '#FFFFFF';
}
else{
isi.parentNode.parentNode.style.backgroundColor = '#66699';
}
</script>

</div>

and

 

CASE
WHEN ATEDIFF(day, [@field:Sub_date], [@field:Deadline]) <= 29 
THEN '<span style="color:red;">'[@field:Deadline]'</span>'
ELSE '<span style="color:#blue;">'[@field:Deadline]'</span>'
END

[BenjaminS]

Anyone solved this?

[Volomeister]

I believe the answer is in this thread: