Just to add to Ruben's solution I think what you need is something like this:
If([Estimated Submission Date]<Today() AND [Request Status] = 'Reserved', 'Yes', 'No') as [No Show]
This satisfies both conditions. I also find it useful to put actual values in place of null values. This allows you to select the null values on the front-end which can be useful if for example someone was interested in records that don't meet that criteria or if you want to conduct some sort of data cleanup exercise.