http://www.functionx.com/bcb/functions/msgbox.htm
This website has more information on what all the arguments are and gives examples how to use them, the only thing is their examples only use 3 arguments you need a fourth argument in the beginning
also you don't need to include any extra header files
here's a quick example
#include "DarkGDK.h"
void DarkGDK ( void )
{
dbSyncOn ( );
dbSyncRate ( 60 );
while ( LoopGDK ( ) )
{
if ( dbSpaceKey ( ) == 1 )
MessageBox ( 0, "MessageBox Text", "MessageBox Caption", MB_OK | MB_ICONWARNING );
dbSync ( );
}
return;
}