Blank Masked Textbox showing selected

Question

Hi,

I have 2 mask text boxes and 2 button on form.
button 1 fill value in mask textbox 1 and button 2
clear value from mask textbox 1.

when I click to button 1 it fill value
in mask textbox 1 when I used tab key then It go to
Masktext box 2 then button according to tab index.

When I used clear button it clear value from mask text box 1
and focus on button 1. when I press tab key again then it goes to Mask
textbox1 which is blank my problem is that text box shows selected
in blue color up to masking limit ie 5 character, even text box  is blank.
I want when masktext box is blank then cursor on first character and
nothing is selected Please suggest how can I do.

Thanks