it seems impossible to enter values with a decimal-comma (used e.g. in Germany) into a numeric field. We're testing the localized version of Designer 7, all the "locale-settings" are set to "German", but entering a value containing a comma leaves the field with "0" in it.
I struggled a long time with this as well... The solution is to supply a localised Edit Pattern e.g. put zzz,zzz.zz in the Edit Pattern. Not the nicest and most logical of solutions but it should work now. No explicit need to change the locale to anything other than Default.
