So I'm starting to expand my 'data' knowledge into relational databases and wondering if there's a google group out there similar to you'se guys. the ones I've found are... inactive to say the least.

Similarly, if someone here could answer that'd be great -
how do I build a new field as a calculation of two other fields?

ex. I have fields Due Date and Completion Date, and I want to take Due Date minus Completion Date (a negative result meaning completion was past due).