how to pass C++ variable in command attribute of button in C++/Tk?

[Jayendra Vyas]

I'm newbie in C++/Tk and want to pass variable which is defined in C++ to command attribute in button.
Herewith I'm posting code snippet.

int eoutputvar ;

stringstream ss ;
string setquery ;

ss.str( "set eoutputvar 10" ) ;
setquery = ss.str() ;

entry(".eoutput") -textvariable(eoutputvar) -width(20) ;

button(".b1") -text("click it") -command( setquery );
pack(".eoutput" ) -side("left") ;

My objective here is to set eoutputvar of entry widget when the button is clicked.