Populate Text Field Using Onmouseover

I have a table where when the cursor passes/hovers over a cell, the current cell, as well as the top cell in its column and the first cell in its row change backgroundColor. I have text fields outside the table which I want to populate with the contents of the cells affected by the mouseover event. So as the mouse moves over different cells, the contents of the text fields changes accordingly. I've got the backgroundColor to change, but when I try to assign the contents of the cells to the text fields, nothing happens. The change of backgroundColor even stops working. This is the code I'm usign to populate the fields.

document.getElementById("tableID").textfieldID.value = Col1Cell[0].innerHTML;
document.getElementById("tableID").textfieldID.value = HeaderCell[n].innerHTML;
document.getElementById("tableID").textfieldID.value = this.innerHTML;

I'm traversing through the <th> and <td> tags to find the header cell HeaderCell[n] and first column cell Col1Cell[0] associated with the current cell. If I leave out these lines the backgroundColor changes, if I use them, nothing happens at all.