Can i make it once someone signs up for a day, that particular day is no longer for others to choose?

Hi, 

If I understand your question correctly, you want to have a list of date available, and once a certain date is selected, it will not be available for selection anymore?

You can make use of our Appointment Slot widget, it will allow you to have a selection and enable you to set a number of available slots, once one slot is selected, the number of available slots will decrease.

Hope this helps, let us know if you need any further help.

Thank you!