As far as I know you can't use either program to preform the math but you can build a simple program in most any language of your choice to take a file use regex to find the number. Cast that string as a double do the math and put it back into the string. Later on today I could probably build something in c# but it should be relatively straight forward in most languages. You may even be able to build a shell script and use grep if you're not in a windows environment or use Powershell for windows but I have less experience with Powershell.
Edit: There is an easier way to do this http://msdn.microsoft.com/en-us/library/hcebdtae(v=vs.110).aspx
this is essentially what you want to do using the xmldocument object.
Edit2: I did this even though I couldn't get a hold of the original poster I thought someone might be able to use the info and I learned a lot. I can add the source code to github if anyone is interested.
public static void ChangePricesWork(string filepath, double multiply)
{
var document = new XmlDocument();
document.Load(filepath);
XmlNodeList nodeList = document.GetElementsByTagName("price");
foreach (XmlNode node in nodeList)
{
if (!string.IsNullOrEmpty(node.InnerText))
{
node.InnerText = Convert.ToString(multiplyPrice(multiply, node.InnerText));
}
}
string newFilePath = string.Format(@"{0}\{1}_updated.xml", Path.GetDirectoryName(filepath), Path.GetFileNameWithoutExtension(filepath));
document.Save(newFilePath);
}
private static double multiplyPrice(double multiply, string oldPrice)
{
var newPrice = new double();
if (Double.TryParse(oldPrice, out newPrice))
{
newPrice = newPrice * multiply;
}
return newPrice;
}