You can insert a line feed / carriage return by inserting 'Chr(13)' in your selection formula in Crystal Report.
For an example,
StringVar textToDisplay := "Title for the Cross-Tab" + Chr(13) + "Period from Year X to Year Y"
For an example,
StringVar textToDisplay := "Title for the Cross-Tab" + Chr(13) + "Period from Year X to Year Y"
Happy Coding!!!