Hello Meir,
You can easily do this using a macro. Here is an example but not including the Capitalize command. You can use this as a start to make it better.
s = document.selection.Text;
if( s.length != 0 ){
n = s.charCodeAt(0);
if( n >= 0x41 && n <= 0x5a ){
s = s.toLowerCase();
}
else {
s = s.toUpperCase();
}
document.selection.Text = s;
}