We have a custom field called "Process Date"
I want to create a view if the date is on or before "Yesterday" but it doesn't seem to have this option.
The only way i have got this kind of working is to use the within the previous 100 days, but this also adds tickets with process date as today.
Has anyone got any ideas on how i can do this?

If you're using a custom date ticket field as a View condition, the only values you can come close utilizing are these two :
- Is within the previous
- Is within the next
These conditions are further explained in this article here.