If my sheet has invalid data trigger dialog box

If my sheet has invalid data trigger dialog box

I used macro recorder to discover ActiveSheet.CircleInvalid which circles
any data that doesn't meet the cells data validation criteria. I linked
the macro to a form control; So far I have:
Sub datavalidationcheck()
ActiveSheet.CircleInvalid
'//Add if there are invalid cells being circled then prompt user with
dialog box
'//else
Application.Dialogs(xlDialogSendMail).Show
End Sub
I am hoping to find out how to make a dialog box appear that requests the
user fix the invalid data. The commented out stuff is the pseudocode for
what I am trying to accomplish.
Thanks