C#

/// <summary>
/// Parses the specified args.
/// </summary>
/// <param name="args">The args.</param>
/// <returns></returns>
public bool Parse(params object[] args)
{
    if ((args.Length > 0) && (args[0] is Dictionary<String, object>))
    {
        _values = args[0] as Dictionary<String, object>;
        //Package destPackage = Package.Open(DestinationPath, FileMode.Create, FileAccess.ReadWrite);
        File.Copy(SourcePath, DestinationPath);
        XpsDocument source = new XpsDocument(SourcePath, FileAccess.ReadWrite);
        XpsDocument destination = new XpsDocument(DestinationPath,FileAccess.ReadWrite);
        XpsDocumentWriter writer = XpsDocument.CreateXpsDocumentWriter(destination);

        //SerializerWriterCollator vxpsd = writer.CreateVisualsCollator();
        //vxpsd.BeginBatchWrite();

        FixedDocumentSequence sequence = destination.GetFixedDocumentSequence();
        foreach (DocumentReference r in sequence.References)
        {
            FixedDocument d = r.GetDocument(false);
            foreach (PageContent content in d.Pages)
            {
                ContainerVisual visual = new ContainerVisual();
                FixedPage page = content.GetPageRoot(false);
                double width = page.Width;
                double height = page.Height;
                Size size = new Size(page.Width, page.Height);

                visual.Children.Add(page);

                foreach(UIElement test in (page.Children[0] as Canvas).Children)
                {
                    if (test is Glyphs)
                    {
                        String glyphContent = processGlyph(test as Glyphs);
                    }
                    if (test is Canvas)
                    {
                        Canvas address = test as Canvas;
                        foreach (UIElement row in address.Children)
                        {
                            if (row is Canvas)
                            {
                                String addres_text = processGlyph((row as Canvas).Children[0] as Glyphs);
                            }
                        }
                    }
                }
            }
        }
        //vxpsd.EndBatchWrite();
        source.Close();
        destination.Close();
        //container.Close();
        return true;
    }
    else
    {
        return false;
    }
}
#endregion

#region Private Methods
/// <summary>
/// Processes the glyph.
/// </summary>
/// <param name="glyph">The glyph.</param>
/// <returns></returns>
private String processGlyph(Glyphs glyph)
{
    String content="";
    String glyphContent = (glyph as Glyphs).UnicodeString.Trim();
    if ((glyphContent.StartsWith("«")) && (glyphContent.EndsWith("»")))
    {
        //Debug.WriteLine(glyphContent);
        String key = glyphContent.Trim(new Char[] { '«', '»' });
        if (_values.ContainsKey(key))
        {
            Glyphs item = (glyph as Glyphs);
            content = item.UnicodeString.Replace(glyphContent, _values[key].ToString());
            item.UnicodeString = content;
            item.Indices = null;
        }
        else
        {
            Glyphs item = (glyph as Glyphs);
            content = item.UnicodeString.Replace(glyphContent, "test");
            item.UnicodeString = content;
            item.ApplyTemplate();
        }
    }
    return content;
}

/// <summary> 
/// Finds the last column on a worksheet. 
/// </summary> 
/// <param name="xlWorkSheet"></param> 
/// <returns></returns> 
public string FindLastColumn(Worksheet xlWorkSheet) 
{ 
int nInLastCol = 0; 

// Find the last real column 
nInLastCol = xlWorkSheet.Cells.Find("*", System.Reflection.Missing.Value, System.Reflection.Missing.Value, 
System.Reflection.Missing.Value, XlSearchOrder.xlByColumns,XlSearchDirection.xlPrevious, 
false,System.Reflection.Missing.Value,System.Reflection.Missing.Value).Column; 

return GetExcelColumnName(nInLastCol); 
} 

/// <summary> 
/// Converts the column # to the corresponding letter. 
/// </summary> 
/// <param name="columnNumber"></param> 
/// <returns></returns> 
private string GetExcelColumnName(int columnNumber) 
{ 
int dividend = columnNumber; 
string columnName = String.Empty; 
int modulo; 

while (dividend > 0) 
{ 
modulo = (dividend - 1) % 26; 
columnName = Convert.ToChar(65 + modulo).ToString() + columnName; 
dividend = (int)((dividend - modulo) / 26); 
} 

return columnName; 
} 

/// <summary> 
/// Finds the last row on a worksheet. 
/// </summary> 
/// <param name="xlWorkSheet"></param> 
/// <returns></returns> 
public long FindLastRow(Worksheet xlWorkSheet) 
{ 
long nInLastRow = 0; 

// Find the last real row 
nInLastRow = xlWorkSheet.Cells.Find("*", System.Reflection.Missing.Value, 
System.Reflection.Missing.Value, System.Reflection.Missing.Value, 
XlSearchOrder.xlByRows,XlSearchDirection.xlPrevious, 
false,System.Reflection.Missing.Value,System.Reflection.Missing.Value).Row; 
return nInLastRow; 
}

Dim TSExcelLib As New TechSolutionsXLLibrary.ExcelFunctions 

Private Sub CommandButton1_Click() 

MsgBox TSExcelLib.FindLastColumn(Sheets("Sheet1")) 'Works 
MsgBox TSExcelLib.FindLastColumn(Sheet1) 'Works 

MsgBox TSExcelLib.FindLastColumn(Sheets("Sheet1")) 'Doesn't work 
MsgBox TSExcelLib.FindLastColumn(Sheet1) 'Doesn't work