How do I make one thing sold out and not the other?

The form I have a question about is for selling event tickets for two different days. We are nearing being sold out for one option, but not the other. How can I make one option sold out while keeping the data information and leaving the other option available? 

Though the option cannot be disabled, it can be hidden from the form with CSS.  Depending on which day you would like to hide, the code would be slightly different.  If July 4th is the day filling up, hiding that day can be done with this code:

http://www.jotform.com/help/117-How-to-Inject-Custom-CSS-Codes

#product-name-input_3_1006,#input_3_quantity_1006_0_0, #input_3_quantity_1006_1_0, #input_3_quantity_1006_2_0, #input_3_1006, #input_3_1006_subproducts span.form-sub-label, #input_3_1006_subproducts span.form-product-child-label {
    display : none;
}

Here is how the form would look with the code added:

http://support.jotform.com/form/61815134023950

On a side note, for new forms, you can actually try using the following widgets that allow for limiting the number of times an option can be selected:

http://widgets.jotform.com/widget/inventory 

http://widgets.jotform.com/widget/quantity_gift_registry 

http://widgets.jotform.com/widget/gift_registry 

http://widgets.jotform.com/widget/ticket_purchases

Then calculate the value of the selections:

http://www.jotform.com/help/301-How-to-Assign-Calculation-Value

And pass that value to the payment field:

http://www.jotform.com/help/275-How-to-pass-a-calculation-to-a-payment-field

This setup would allow you to control the number of tickets/products available and disable the option once that limit is reached.