Get the previous of previous frame's WPO.

Development Programming & Scripting
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1

Hi, I am doing a test in 5.1.1 to try to get the WPO velocity not only just from previous frame but from the previous of previous frame, that is to say, to get a skip frame velocity.
I checked the material and think I might need to expand this material shader entries from

enum ECompiledMaterialProperty
{
	CompiledMP_EmissiveColorCS = MP_MAX,
	CompiledMP_PrevWorldPositionOffset,
	CompiledMP_MAX
};

to

enum ECompiledMaterialProperty
{
	CompiledMP_EmissiveColorCS = MP_MAX,
	CompiledMP_PrevWorldPositionOffset,
    CompiledMP_PrevWorldPositionOffset_1,
	CompiledMP_MAX
};

But I couldn’t find the place where CompiledMP_PrevWorldPositionOffset value is set to MP_WorldPositionOffset, also the material template is so complex and it seems Unreal only have a <prev> prefix to replace.

So my question is that is it possible to get this done? and how? will be appreciate for any hint.