I have used TK Spinbox to select different units. when the user changes the unit, my perl script should change the entire number to the 'user selected unit'. so i would like to know what was the unit BEFORE change and what is it CHNAGED to. using this i can convert the numbers to rigth unit. See the code below 
$u1 = $mw->Spinbox(-values => [qw/Mil MM Inch/],-exportselection=>STRI
+NG, -textvariable=>\$dtm_unit,  -width => 5,-command=>\&change_unit )
+->grid(-row=>1,-column=>2 ,-sticky=>"ew");

[download]
when this perl script s run all numbers will be in Mil(1/1000 of an inch) when user rolls the spinbox to MM, all numbers should be converted from Mil to Milimeters(MM), when user rolls spinbox again then all numbers in MM should be changed to Inch. likewise if user rolls down the unit to MM then numbers should be converted from Inch to MM. now i can get the CHANGED (New) unit, but am unable to check what was it BEFORE change. is there a way to capture the previous unit in this example? i used spinbox just for convenience. i am open to other TK widgets such as Radiobutton, Optionmenu etc, any idea?

In reply to Previous Selection in Spinbox by shreedarasp

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