A simple way is to exit the sub if an error condition is found:
Private Sub cmdCheck_Click()
If IsNull (Me.RevDate) or Me.RevDate = "" Then
MsgBox "You must enter a review date", vbOKOnly, "Required Data"
Me.RevDate.SetFocus
Exit Sub
End If
If IsNull (Me.ProvCd) or Me.ProvCd = ""...