Change XML Value in an existing XML BLOB (Report Parameter)

Good Evening guys,

I want to Change a Report Parameter befor Executing The Report. The Report will execute automaticlly start by the Job Queue, but some Report Parameter have to be calculate every Time, for example the Reference Month.

The Report Parameter are saved in a blob Field, which will be read before Executing. Some of These Parameter should be Change before executign the Report.

I know the XML Node (ReferenceMonth), i can get the Saved Value, but i dont know how to Change this value.

Below the Function for get the XML Value:

GetNodeValueOfXMLParameters(XMLText : Text;NodeName : Text) : Text
IF XMLText = '' THEN
EXIT('');

XMLDoc := XMLDoc.XmlDocument;
XMLDoc.LoadXml(XMLText);
XMLNode := XMLDoc.SelectSingleNode(STRSUBSTNO('ReportParameters/Options/Field[@name=''%1'']',NodeName));
IF ISNULL(XMLNode) THEN
ERROR(NodeNotFound);

IF STRLEN(XMLNode.InnerText) > 0 THEN
EXIT(XMLNode.InnerText);