This example shows how to use the Formula child element to create a custom VML shape.
<!-- Include the VML behavior -->
<style>v\:* { behavior:url(#default#VML);display:inline-block }</style>
<!-- Declare the VML namespace -->
<xml:namespace ns="urn:schemas-microsoft-com:vml" prefix="v" />
<v:shape style="width:1in;height:1in;" strokecolor="red" strokeweight="2pt"
coordsize="21600,21600" adj="17520"
path="m10800,0qx0,10800,10800,21600,21600,10800,10800,0xem7340,6445qx6215,7570,7340,8695,8465,7570,7340,6445xnfem14260,6445qx13135,7570,14260,8695,15385,7570,14260,6445xnfem4960@0c8853@3,12747@3,16640@0nfe">
<v:formulas>
<v:f eqn="sum 33030 0 #0" />
<v:f eqn="prod #0 4 3" />
<v:f eqn="prod @0 1 3" />
<v:f eqn="sum @1 0 @2" />
</v:formulas>
</v:shape>