[2005] Insert value using RegEx

I have a complicated HTML div tag below and I need to add the line

background-image: url(http://download.skype.com/share/skyp...ppet_top.png);

in the <H1 tag as I have shown below....

only if it does not exist in the code. Can anyone help me do this one? Thanks....

Code:

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<div id="Div1" style="width: 160px; overflow: hidden; padding-right: 0px;
                background-position: left top; padding-left: 0px; background-attachment: scroll;
                padding-bottom: 0px; padding-top: 0px; background-repeat: no-repeat; background-color: #00aff0;">
            <h1 style="color: white !important; font: 16px/1.4 Arial, sans-serif; font-weight: bold !important;
                margin: 0 !important; padding: 10px 10px 2px 10px !important; background-image: url(http://download.skype.com/share/skyp...ppet_top.png);">
                Adobe Certified Professional</h1>
            <p style="color: white !important; font: 10px/1.3 'Lucida Grande', Verdana, sans-serif !important;
                font-weight: bold !important; padding: 0 10px 2px 10px !important; margin: 0 !important;">
                Providing assistance in (X)HTML, CSS, usability, web standards and accessibility. Speaking French and English.</p>
            <a href="http://www.skype.com/go/joinskypeprime?call&skypename=emac2damien" title="Use Skype to call now"
                style="height: 32px !important; display: block !important; font: 16px Arial, sans-serif !important;
                font-weight: bold !important; text-decoration: none !important; background: transparent url(http://download.skype.com/share/skyp...pet_button.png) top left no-repeat !important;
                padding: 0 5px 0 50px !important; margin: 10px 10px 0 10px !important; color: #0083b3 !important;
                line-height: 32px !important;">Call now</a><p style="margin: 10px 0 5px 0 !important;
                    color: white !important; font: 10px/1.3 'Lucida Grande', Verdana, sans-serif !important;
                    font-weight: bold !important; padding: 0 10px 0 10px !important;">
                    0.99 € / min</p>
            <div style="margin-top: 0 !important; background: #00aff0 url(http://download.skype.com/share/skyp...pet_bottom.png) bottom left no-repeat !important;
                padding-top: 13px;">
                <div style="float: left !important; width: 10px !important; height: 20px !important;">
                </div>
                <a href="http://www.skype.com/?cm_mmc=skype-_-public-_-snippet-_-tag" style="display: block !important;
                    float: right; height: 20px !important; width: 50px !important;" title="Free international calls when you call friends on Skype">
                </a>
                <div style="clear: both !important;">
                </div>
            </div>
        </div>

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