[WJG] 10th June, 2005. Why doesn't the BWidget ComboBox does have a 'built-in' means of updating the selection list from  data validated in its entry box. Perhaps, it has and I haven't looked hard enough. Anyway, it was quicker to just cook something up. So here's my offering.

# -------------------------------------------------------------
# ComboBox_history.tcl
# Written by William J Giddings, 2005
# -------------------------------------------------------------
# 
# Purpose:
# --------
# To provide history for the BWidget ComboBox. 
# 
# Note:
# -----
# * This is not achieved by manipulating the BWidet code but by 
# simply providing a suitable proceedure to be called when the 
# entry subwidget is validated.
# * New vallidated entries are placed at the top of the list.
# * Duplicate entries will not be added.
#
# Use:
# ---------------
# ComboBox .cmb -values {A B C} -command _h
#
# -------------------------------------------------------------

# -------------------------------------------------------------
# a simple handler, no args required
# -------------------------------------------------------------

proc _h {} {  
    set w [winfo parent [focus]] 
    set a [$w get]
    set b [$w cget -values]
    #check to see if value already there..
    if { [lsearch -exact $b $a] } { $w configure -values "$a $b"} 
}

# -------------------------------------------------------------
# the uniquitous demo!
# -------------------------------------------------------------
proc demo {} {
    package require BWidget
    pack [ComboBox .cmb -values {A B C} -command _h]
}

demo