CAD tip # 8669:

E.g. you need to add a 1.75mm module to the DIN 5480 offering - specifically the size 62 mm - 1,75 x 34. For this change you will need to modify three XML files: DIN5480-30.xml, DIN5480-30_In.xml and DIN5480-30_Out.xml and add the missing size values. You can find these files in the Inventor's "Design Data" folder, specifically in:

C:\Users\Public\Documents\Autodesk\Inventor 2013\Design Data\Design Accelerator\Tables\SplinesInv\.