Knockout array references

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Knockout.js

I want to keep track of an item in a 2D array (think along the lines of cell with focus).

However I am either very sleepy or incapable of googeling a good answer.. (or both)...

here is roughly what I was trying to do:

   function ViewModel() {
    var self = this;
    self.data = get2Darray();
        self.currentItem = {???};
    self.itemDetails = ko.computed(function () {
        return self.currentItem.blah +self.currentItem.blah2;
    });
        self.getNext = ko.computed(function () {
        self.currentItem = self.data(--{Next}--);;//???
    });
};
ko.applyBindings(new ViewModel());

with html:

<div  class='mazeRow' data-bind="foreach: data" >
     <div data-bind="attr: { 'class': fuzzy }"></div>
</div>
<input type="button" id="Button3" 
       data-bind="click: btn_Click, enabled: currentItem.enabled"        
       value="FraggelRock"/>

<input type="button" id="Button4"  data-bind="click: getNext" value="move Next"/>

What am I doing wrong?