Question : Windows Application textbox.focus

I have a windows app that requires validation of a datefield like so

if date is incorrect format
MessageBox.Show("Date must be a valid Date format MM/DD/YYYY");
D_textboxLabel4.Focus();

if I enter the incorrect format the messagebox displays but it seems to be stuck in a continous loop.

what I need is...user sees the message box, clicks ok, box dissappears and user is able to correct mistake...currently box does not disappear.

Answer : Windows Application textbox.focus

if it is a textbox then

....
If Not IsDate(Cdate(String.Format("dd/MM/yyyy",myTextbox.text))) then
Messagebox.show(.......)
MyTextbox.selectAll
end if