Mouse Scroll over winow caption but not active

[ken gray]

I have a function that will lower (and raise) the transparency when I scroll the mouse wheel when over the window's caption.  I'd like for it to work on the non-active window as well.
How can I do this?

Function Trans_Lower
Trigger #Dh2 0x1     

Code:

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dll user32 #GetLayeredWindowAttributes hwnd *crKey !*bAlpha *dwFlags
int col flags; byte alpha
int z
GetLayeredWindowAttributes win &col &alpha &flags
z=18
if alpha=0
,alpha=255
else
,alpha-z
;out "alpha %i" alpha
if alpha<18
,bee "C:\downloads\sounds\system\comp3.wav"
,Transparent(win 25)
,3
,end
Transparent(win alpha)