This is a page for longer things that I'm not sure whether or not belong on the Wiki or how to categorize them.  In hindsight I maybe should have used the name chat temp.  Oh well...  
----

 #GPS
 proc blink.me {win i} {
  set cur [$win curselection]
  set fg [$win cget -foreground]
  set bg [$win cget -background] 

  foreach {bg fg} [list $fg $bg] break
  $win configure -foreground $fg
  $win configure -background $bg
  incr i 
  if {$i > 5} return
  after 50 [list blink.me $win $i] 
 }
 pack [listbox .l]; .l insert end Hello World
 bind .l <<ListboxSelect>> {blink.me %W 0}

hmm...  Now that was a little annoying.  It flashes too much.  Let's make it only flash 2 colors or maybe even 3 and then reset.  I think passing it a list of colors might work better.

 #GPS
 proc blink.this {win colList i} {
  set cur [$win curselection]
  foreach {bg fg} $colList break
  $win itemconfigure $cur -selectforeground $fg -selectbackground $bg
  incr i 
  if {$i > 5} {
   $win itemconfigure $cur -selectforeground {} -selectbackground {}
   return
  }
  after 50 [list blink.this $win [list $fg $bg] $i]
 }

 pack [listbox .l]; .l insert end Hello World this is George!
 bind .l <<ListboxSelect>> {blink.this %W {red blue} 0}

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Abhishek I hope this helps:

 #! /bin/wish8.3
 proc toolbar:make {win arPtr} {
	upvar $arPtr ar
	set i 0; 
	foreach {name mem} [array get ar] {
		set img [lindex $mem 0]
		set cmd [lindex $mem 1]
		pack [button $win.$name -image $img -command $cmd] -side left
		incr i
	}
 }

 proc toolbar:disable {win arPtr key disFile} {
	upvar $arPtr ar
	set img [lindex $ar($key) 0]
	$img read ./$disFile
	$win.$key config -state disabled
 }

 pack [frame .f -relief groove -bd 1]
 set ar(hello) [list [image create photo -file ./hello.gif] {puts "Hello World"}]
 set ar(goodbye) [list [image create photo -file ./goodbye.gif] exit]
 toolbar:make .f ar


 pack [button .b -text "Disable Hello" -command {toolbar:disable .f ar hello ./goodbye.gif}]