Is there a way to get the Condition Editor to recognize elements that are Selected?

We do not have a criteria in display rules to recognize "Selected" elements.

Display Rules can change element visualization on draw, not modify or select elements

For this you can use Explorer search:

1. Select Advance Search 

2. In Search for: type sphere for example

3. Select Where: volume for example

4. Change equal for less than

 5. Type on the box for  example: 40 m³

6. Select add to search and press ok

7. Select again Where: volume

8. Change equal for Greater than

 9. Type on the box for  example: 2 m³

10.  Select add to search and press ok

and then you will get this new search in  the explorer tool

11. Select Elements\ Sphere from Explorer do right click and select Delete elements

See video

See Also

http://communities.bentley.com/products/microstation/w/microstation__wiki/23718.how-to-select-elements-using-a-range-of-values-greater-than-and-less-than-in-order-to-delete-them