About Windows: what i need to know before simulate the keys?

[Cambalinho]

i build a program for execute(ShellExecute() ) another program. then i change window position program(SetWindowPos() ).
until here fine, but i need to know 2 things:

1 - when we use ShellExecute(), can we Wait until the program window is ready for simulate the keys?

2 - sometimes i fail, without any error message, using the SetWindowPos(). i belive i know why i fail, but i need a correction: if the window program isn't ready, what happens with SetWindowPos()?
(if i use Sleep(2000) between the 1st and second, the SetWindowPos() will works normaly.

[Thomas1965]

if the window program isn't ready, what happens with SetWindowPos()

Check the return value from SetWindowPos and call GetLastError() if neccessary.

[Cambalinho]

is zero. seems that i must wait that the window is ready or something because the:
CTRL+1 or even CTRL+2 makes the window hide and then show it.
so if i use the SendInput() and then the SetWindowPos(), with GetForegroundWindow(), the SetWindowPos() must fail, right?(because can do the job to another window)