regex to match whatever between

Please, i need some help to create the right regex

<script type="text/javascript">Decode("2%65%66%_WHATEVER_8%74%74")</script>

I want to detect whatever between Decode(" ") to give me this output 2%65%66%_WHATEVER_8%74%74

I tried a lot, but nothing work correctly to give me the exact output that i want.