Automatically click an element of a toolstrip

Question

Im triying to automate the control of a program. I want to load a big amount of files automatically.

The program loke like this (winspector view and and corresponding api view):

As you can see, I have 7 element in my toolstrip. What I want to do is to figure out some way to click the desire element of this toolstrip (lets call the "n" element)

By doing this:

'lhWndP is the parent window handle
toolstriphandl= FindWindowEx(lhWndP, 0&, "WindowsForms10.Window.8.app.0.378734a", "toolStrip1") 

I get the handle of the toolstrip, but I dont know what to do now.

I tried to do this:

toolstripmenu = GetMenu(toolstriphandl)
toolstripmenu = GetSubMenu(toolstripmenu, n)
SendMessage toolstriphandl, WM_COMMAND, toolstripmenu, 0

But doesn't seems to work.

Any idea please? Im desperate with this.

Thank you.