Quality control charts are important and helpful tools of internal quality control in analytical laboratories. The ExcelKontrol is an Excel® macro intended for the daily operation of quality control created by Michael Koch from the University of Stuttgart. With this you may operate x-charts, r-charts, r%-charts, blank charts, differences charts and recovery charts. The charts may be used as with statistically determined limits or with target charts. In the latter case the limits are defined by external quality requirements independent from the data. The sheets can be found here.
We strongly recommend using target control limits - see the Trollbook.