Easy Function

I know this should be an easy one but ive been busting my butt looking for a solution.
I am trying to pull an external jpg file into a new window using different buttons. I know there is a way to assign a function to each button for just the file path then I dont have to copy and paste all the code to open up the window.
I created the function changepic() you can see where i want to insert the path in "test picture 1". "test picture 2" shows the path without calling the function. I have the button code at the bottom. Any assistance would be greatly appreciated.
Thanks for your time. I know im doing something stupid.

import mx.managers.PopUpManager;
import mx.containers.Window;
function changePic() {

}

var issueLocation:Boolean = true;
function toggleCity() {
var currentArea:Number;
if (issueLocation) {
currentArea = 0;
issueLocation = false;
var my_win = mx.managers.PopUpManager.createPopUp(_root,
mx.containers.Window, true, {title:"test picture 1",
closeButton:true,contentPath:changePic()});
my_win.setSize (800,600);
var winListener:Object = new Object();
winListener.click = function() {
my_win.deletePopUp();
};
my_win.addEventListener("click", winListener);

} else {
currentArea = 1;
issueLocation = true;
var my_win = mx.managers.PopUpManager.createPopUp(_root,
mx.containers.Window, true, {title:"test picture 2",
closeButton:true,contentPath:"pics/test.jpg"});
my_win.setSize (800,600);
var winListener:Object = new Object();
winListener.click = function() {
my_win.deletePopUp();
};
my_win.addEventListener("click", winListener);



// location for future code to calculate Payoff from mySQL
}

}

button_btn.onPress = function() {
toggleCity();
changePic("pics/test.jpg");

}