Static Leading Character + 5 Numbers.

Is it possible to use MaskedEditExtender with a initial static value?
<asp:MaskedEditExtender ID="MaskedEditExtender3" runat="server" TargetControlID="txtCode" MaskType="Number"
Mask="C99999" AutoComplete="false" ClearMaskOnLostFocus="false" >     </asp:MaskedEditExtender>

I would like this to return A_____ where A is a static value and there are 5 spaces for numbers.