Dennis @ PerfectForms
Use a hidden helper (month). When the date input changes data populate the helper with the month value. Then use that month as a send parameter to the form connection. You will have to modify your form connection to use the month field as a send parameter. Return any value to a hidden helper table (use a meta-data field so you know there is a value for every matching instance). Then use a set field with a sum function to give you the number of rows in the table.