Creating a Conditional Formula in Crystal Reports

Hi

I was hoping someone could help me write a conditional formuala for a report.

The report layout and data is entered as follows:

Start Date               End Date                   Absence Reason              RTW?

11 June 2013          15 June 2013               Sickness                              Yes

I want to be able to run a report that only shows a value in the "End Date" field if "RTW?" equals Yes, if "RTW?" equals No,  I want the "End Date" field to remain blank.  Can anyone help me write the fomula to do this.

thanks

Loula1978