This doesn't solve my problem; it doesn't simulate clicking (tapping) on the day. I solved it this way:
I created a sub called selection, and inside it I put the code from the sub AS_DatePicker1_SelectedDateChanged(Date As Long). When called by a click, it calls the selection sub. Then I put the code you gave me at the end of the AS_DatePicker1_CustomDrawHeader sub, calling the selection sub.
maybe a little cumbersome but it works, anyway thank you all