send message to button of a window

Sounds like you're up to no good. Use GetParent to get the parents handle, the use GetWindowText to get the caption.  You already have the name of the checkbox?  If you mean the class name, you can use FindWindowEx using the other information you have to get the checkbox handle.

Then, with the handle of the checkbox, you can use SendMessage.  Sorry I don't have more info or code, but this should help you along a bit, and all the functions are fully documented in MSDN.

Have fun.

i've tried that it doesnt work
i need to click the mute all checkbox in the volume control of the windows

Check out the following link:
http://www.axter.com/faq/topic.asp?TOPIC_ID=35&FORUM_ID=4&CAT_ID=9&Topic_Title=Controlling+Another+Program&Forum_Title=C%2FC%2B%2B

It has a wrapper class that does what IainHere stated above.

My word! You went to all that trouble for 50 points!  Very impressive - I think I'll give up :)

std::vector<WindowPath> windowpath1;
windowpath1.push_back(WindowPath("Volume Control","",0));
windowpath1.push_back(WindowPath("","&Mute all",0));
Ext_Wnd VolumeControl(windowpath1);

IainHere,
Didn't you see the date on the link.  That's an old class I created a couple months ago for another project.

etay,
On my previous comment, I posted example code for getting the window handle for the Mute-All checkbox on the Volume Control.

If I had time, I would show you how to send the check message.
If IainHere or none of the other experts haveing givin you the additional information by the time I get back, then I'll posted it for you.

It should be something like the following:
VolumeControl.SendMessage(???,???,???);

If you have a handle on the checkbox, use:

<from msdn under BM_SETCHECK>

SendMessage(
  (HWND) hWnd,              // handle to destination window
  BM_SETCHECK,              // message to send
  (WPARAM) wParam,          // check state
  (LPARAM) lParam          // not used; must be zero
);

in order to set it, you'd use

SendMessage(hwndMuteAll, BM_SETCHECK, BST_CHECKED, 0);

Hope this helps.  Also, "i've tried that it doesnt work" - which bit doesn't work?

Axter:  I was trying to suggest that you'd created the website specifically to answer this question.  Sorry I didn't make it more clear.  Or funny.

Axter,

>>Didn't you see the date on the link.  That's an old
>>class I created a couple months ago for another
>>project.

Don't give me that!  Give yourself full credit.  You ANTICIPATED that this question would come up and proactively created this example so you'd be ready...

Right??

jhance,
>>Don't give me that!  Give yourself full credit.  You
>>ANTICIPATED that this question would come up and
>>proactively created this example so you'd be ready...
>>Right??
Ok, I must confess.  I did create the class for a personel project, but I posted it on the web because I see this question asked so many times in EE.
Thought it be easier to answer with wrapper class.

Though I need to add some more examples to it.