javascript doesnt work after using the "save as other" menu

i have a pdf file with javascript, the code works perfectly as long i´m working in the file, but when i use the "save as other/reader extended pdf/enable more tools" and i open the new file, the code no works at all.

i use the javascript console and i got this message:

ReferenceError: showCharCount is not defined

1:Field:Keystroke

i´m using this code to get the character count of a field:

in the fields from which I need to take the count, in the custom keystroke script:

showCharCount();

in a second, thirtd and fourt field (this fields are not visible to the end user, it is only for the following function):

// Document level function 

function showCharCount() { 

    // gets whats on the field 

    var num = AFMergeChange(event).length; 

    // show characters 

    getField("count").value = num; 

}

and finally in the "totalcount field":

// Set the minimum number of characters 

    var min = 1900;

event.value = ( this.getField("count").value + this.getField("count2").value ) + this.getField("count3").value + this.getField("count4").value;

// Set the value of the other text field to show how many character have been entered 

    getField("totalcount").value = event.value + " of " + min;

i got no background in programming so i really don´t know what i´m doing wrong.

P.S.

sorry, my english is not so good