Thank you, I have solved this problem.

yes,i am sure.

Hello, can you understand what I said now ??

A.exe is my own program,B.exe is not my own program. B.exe has a button, click it, and will call to EXCEL! Now, my question is: if click this button to manually, EXCEL will be normal calls.---(OK) But if use my program(A.exe),the Sendmessage function sends a keystroke messages (WM_KEYDOWN WM_SYSKEYDOWN) on the button, EXCEL will call fails.---(NG) I'm sure it: Sendmessage function keystroke messages is sent successfully!

Sorry, I am the only one，incidentally, I'm Chinese.English is not our official language，I tried again to translate。

sorry,my english is not good enough.

why?

External program used excel, if you click on the click of a button to send a message through the simulation, excel this call can not be started. If my program is A.exe I need to simulate an external program control after clicking B.exe this B.exe a button click can not call excel Case 1: B.exe manually click a button in excel can be a normal call! --OK! Case 2: using the SendMessage function to send a message with A.exe analog control click on the button in excel B.exe call fails, and pop-up "can not start Excel server!"! --NG! Messages sent using SendMessage is successfully sent, message "Unable to start Excel server!"! Also shows that the message was sent successfully, but it is not up calls excel! Question: permissions problem? Or anything else that needs to feed?