* when it exists. Create it with the given value when unexistant.
* A copy of the binArea is made to be kept in the Document.
* @param binArea (binary) value to be set
* @param group Group number of the Entry
* @param elem Element number of the Entry
* when it exists. Create it with the given value when unexistant.
* A copy of the binArea is made to be kept in the Document.
* @param binArea (binary) value to be set
* @param group Group number of the Entry
* @param elem Element number of the Entry