highlight text when field has the focus

Hi,

By default, I have a few text boxes that have 0.00 in them. When I tab to these text boxes, sometimes the 0.00 is highlighted, allowing me to type over the existing numbers, but other times it leaves the curser before the first 0. How can I always have the numbers highlighted in the textbox when it has the focus, so I can just overwrite the existing number.

Thanks,

Dave
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