on the lost focus event of maskedtextbox i made a code that

if maskedtextbox1.text = "" then
msgbox("enter your number")

BUT as focus losts so it does not give message, because masked textbox is not empty because when we give mask so it uses " - " in it. so please assist me in this that what code i write to solve this problem.?

mask is 00000-0000000-0