checking the value of textbox in tab out.

Hi,

 i have a textbox,
<asp:textbox id="Txt_QtnBaseEML" Width="128px" Runat="server"></asp:textbox>

when the user tab out of this textbox, i shud check for the value entered in textbox.
1 -  If the value is <= 25, i shud show them a alert message with "OK" button in it.
2 -  If the value is not between or equal to 1 to 100 then, show them a message with "OK" button On clciking the "OK" button. the value entered in textbox shud be removed automatically.

URGENT,

Thanks..