Grid not reflecting new values?

I have a Javascript function (this post is a continuation from another post that I have since resolved) that uses an Infragistics UltraWebGrid control. My problem is that after a function call is made to format some data, the cell in the grid won't reflect the newly formatted values. My code is below:

Code:

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function UG_MarketStatis_AfterCellUpdateHandler(gridName, cellId) {
    var cell = igtbl_getCellById(cellId);
    var grid = igtbl_getGridById('UG_MarketStatis');
    var row = cell.Row;
    var marketData;
    var column = cell.Column;

    if (column.Key == "Market_Data_Amt") {
        var iID = row.getCellFromKey("ID").getValue();
        document.getElementById("h_val").value = row.getCellFromKey("Market_Data_Amt").getValue();

        if (iID == 1) {
            FormatPercent(document.getElementById("h_val"), 2);
        }
        else {
            FormatCurrency(document.getElementById("h_val"), 2);
        }
        marketData = document.getElementById("h_val").value;
        alert('marketData is ' + marketData);
        row.getCellFromKey("Market_Data_Amt").setValue(marketData);
    } 
}

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The "Alert" statment actually shows the correct value that should be displayed in the grid cell, however, the next line of code will not show the formatted value. This particular column is defined as a System.Double, hence accepting numeric values only. I have even tried using the "document.getElementById("h_val").value" in place of the "marketData" variable and I still get the same results. I've been working on this for hours with no luck.

Thanks,