try {
XMultiServiceFactory oDocMSF = (XMultiServiceFactory)tParam.getMSF();
XInterface FA = (XInterface)oDocMSF.
createInstance("com.sun.star.sheet.FunctionArgument");
FunctionArgument arg = (FunctionArgument)AnyConverter.toObject
(FunctionArgument.class, FA);
arg.Description = "FunctionDescription argument description" ;
arg.Name = "FunctionDescriptiuon argument name" ;
arg.IsOptional = true ;