Create an option menubutton and its menu.
http://purl.org/tcl/home/man/tcl8.4/TkCmd/optionMenu.htm
The code for this command is found in Tk's optMenu.tcl library file.
See also: optionMenu.
SYNOPSIS
tk_optionMenu w varName value ?value value ...?
DESCRIPTION
This procedure creates an option menubutton whose name is w, plus an associated menu. Together they allow the user to select one of the values given by the value arguments. The current value will be stored in the global variable whose name is given by varName and it will also be displayed as the label in the option menubutton. The user can click on the menubutton to display a menu containing all of the values and thereby select a new value. Once a new value is selected, it will be stored in the variable and appear in the option menubutton. The current value can also be changed by setting the variable.
The return value from tk_optionMenu is the name of the menu associated with w, so that the caller can change its configuration options or manipulate it in other ways.
EXAMPLE
tk_optionMenu .menu globVar Val1 Val2 Val3 ValJunk pack .menu
To put the contents from a list
set l {4 5 6}
set optname [tk_optionMenu .menu varname junk ]
pack .menu -side left
$optname delete 0
set j [llength $l]
for {set i 0} {$i < $j} {incr i} {
set e [lindex $l $i]
$optname insert $i radiobutton -label $e -variable menvar -command {global menvar; set varname $menvar}
}Do you want "an event binding for selecting a value from tk_optionMenu"?
Tom Wilkason pointed out in a comp.lang.tcl thread that "The most common approach is to have a trace on the linked variable."
Tk syntax help - Arts and Crafts of Tcl-Tk Programming - Category Command