Selectbox in wordpress theme options

I am currently creating some theme options in wordpress & I am trying to create a select box so the user can select a skin to use for the theme. I am new to wordpress theme options so I don't know a lot about them.

I am in need of some help with the php so that when the user selects one of the options it updates that option with selected="selected" & saves it and then the value of that option is sent to the header.php file so i can use it from there.

HTML Select I am using

<select>
    <option value="" selected="selected">Select a skin</option>
    <option value="light.css">Light Skin</option>
    <option value="dark.css">Dark Skin<开发者_如何转开发;/option>
 </select>

Thanks for any help!

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Could not create a query to add the selected="selected"

for example:

<select>
    <option value="">Select a skin</option>
    <option value="light.css" <?php if($theme == $themename):?>selected="selected" <?php endif; ?>>Light Skin</option>
    <option value="dark.css">Dark Skin</option>
 </select>

You would add this to all <option> elements