Hi,
You would need to create a custom macro in which you can access fields that user has submitted and based on the value of the first name, you can return any text you need. You can use the following code in the custom macro to get the first name:
IDataContainer data = e.Resolver.SourceData[0] as IDataContainer;
string firstName = ValidationHelper( data.GetValue("FirstName"), String.Empty );
More information about creating a custom macro can be found here:
Types of macrosBest regards,
Michal Legen