the arg1 of <OnClick> event

[xmlover]

CODEs in XML

<OnClick>
       MIEasyOpen_Show(arg1);
</OnClick>


CODEs in LUA

function MIEasyOpen_Show(arg1)
	if (arg1 == "RightButton") then
		Frame1:Show();
	elseif (arg1 == "LeftButton") then 
		Frame2:Show();
	end
end

i wanna a button,when i left click it ,it shows Frame2.and shows frame1 when i right click it.

But it seems that the arg1 returns from <OnClick> never check the RightButton of the mouse but only the left button


why?

how to fix it ?