Image Onclick Change Drop Down Value

i have a drop down menu called DDvehAttr

there are 7 values in this drop down (which is preloaded via backend) and the values are 1-7.

when the user clicks on an image i would like to alter the selected value in the DDvehAttr drop down with an onclick event.

there are 7 images in total and i would hope to do something like the following:

Code:
<img value="choice1" onclick="changevalue()" />
<img value="choice2" onclick="changevalue()" />
<script>
Function changevalue()

[Code]....