One of the key points during my session at the CRMUG – Mastering Calculated and Rollup Fields was the importance of planning ahead before jumping into creating fields and using the wizard.
I didn’t bring it up during the session but here is another example of how critical this is to not only the first user experience but to your ongoing data integrity.
Once you create a Calculated or Rollup Field you cannot change the Minimum/Maximum Values. If your field doesn’t allow the complete range of values that could be produced from the underlying fields to be submitted the Save event will fail. Once you get into that situation it will be necessary for you to remove the current Wizard driven field and go back to creating a new one. This will of course reek havoc on your views and reports that rely on the Calc/Rollup Field.
Here is an example of where the Calculated field didn’t allow for the sum of the two fields to be less than Zero.