Vml clipping mask

Am I trying to create a clipping mask in VML that matches clip-pathin SVG? Is it possible?

Based on numerous, but rather limited examples, I tried to draw a form:

<vml:group style="WIDTH: 1px; HEIGHT: 1px" class=vml-element coordsize = "1,1">
    <vml:shape style="WIDTH: 1px; HEIGHT: 1px" id=vectorObject2 class=vml-element _fill-color="red" _fill-opacity="1" _stroke-color="black" _stroke-opacity="1" _stroke-width="1" coordsize = "1,1" filled = "t" fillcolor = "red" stroked = "t" strokecolor = "black" strokeweight = ".75pt" path = "m0,0 l100,0,0,100 xe">
        <vml:fill class=vml-element opacity = "1"></vml:fill>
        <vml:stroke class=vml-element opacity = "1"></vml:stroke>
    </vml:shape>
</vml:group>

and then masking it with vmlframe:

<vml:vmlframe class=vml-element clip = "t" size = "15pt,37.5pt" src = "#vectorObject2">    </vml:vmlframe>

The shape drawing (triangle) works as expected, but I cannot find a way to mask it with vmlframe . Is this the right way to achieve camouflage?

Please ignore the whole bunch of weird user attributes as most of the VML code was generated through a third-party library.

Thanks in advance!