Query String Parameters

I am looking for the best method for user experience to indicate a string is required if another parameter is not passed. This I would describe as “Conditional Required” anyone else find a clever way to do this for the user experience?

For example:

start_date

string

show appointments that start between the start_date and end_date

Required

end_date

string

show appointments that start between the start_date and end_date

Required

date

string

show specified date

Required If Start Date End Date not present