How To Bind UBorder Events?

I’m creating a UBorder control through code and can bind the OnMouseButtonDownEvent:

        UBorder* border = NewObject<UBorder>(this, UBorder::StaticClass());
        border->OnMouseButtonDownEvent.BindUFunction(this, "MouseDown");

But I’m having difficulty in finding what the parameters are to the callback function.

Does it have any? Where can I find documentation for it?

I’m trying to take action in my callback code based on which object was selected but I can’t tell what it is at this point.

Thank you.

With a different syntax and signature I can get the FGeometry of the control, but I cannot access the control itself:

.h
UFUNCTION()
FEventReply MouseDown(FGeometry geo, const FPointerEvent& fevent);

.cpp
{
:
UBorder* border = NewObject<UBorder>(this, UBorder::StaticClass());
border->OnMouseButtonDownEvent.BindDynamic(this, &UMyScreenWidget::MouseDown);
:
}


FEventReply UMyScreenWidget::MouseDown(FGeometry geo, const FPointerEvent& fevent)
{
    return FEventReply(false);
}

But I can’t get to the UBorder that is associated with the event.

Does anyone know what I’m doing wrong?