I haven't done it that way. If you know that you are going to create a field, just create the field. When designing the report, you need to specify the data structure, in the case of a ADO.Net dataset, you would create a XSD file and create a Crystal connection to it. When you do, the tables and fields in the dataset are available to you at design time.
If you ran your sql with the Times7 field, the report would fail because it is looking for a column in the table that doesn't exist.
What I do, is create my SQL statement in a stored proc. My app then calls the stored proc and returns a dataset. I stop the program and have the dataset write itself and the schema to the XSD file. I then create the report using the XSD file...it is just like connecting to a table, all the columns and sample data are there. When the report is done, I save it and have the application call the report.
Any changes in the data structure are handled the same way. I get the dataset, write it out, and use this file to modify the existing report.
I hope this answers your question.