String parameter too long.' c#

// Find text 
Range range = doc.Content;
range.Find.Execute(findText);
// Define new range 
range = doc.Range(range.End + 1, range.End + 1);
range.Text = "new text...";

// Find text 
Range range = doc.Content;
range.Find.Execute(findText);
range.Text = "new text...";