diff --git a/util/format.py b/util/format.py
index 7a7f780..2a0f911 100644
--- a/util/format.py
+++ b/util/format.py
@@ -50,10 +50,11 @@ def formatDate(dt=None, type='date', variant='medium', lang='de'):
     return fmt.format(dt or datetime.now())
 
 
-def formatNumber(num, type='decimal', lang='de'):
+def formatNumber(num, type='decimal', lang='de', pattern=u'#,##0.00;-#,##0.00'):
     loc = locales.getLocale(lang)
     fmt = loc.numbers.getFormatter(type)
-    return fmt.format(num)
+    return fmt.format(num, pattern=pattern)
+
 
 
 def toStr(value, encoding='UTF-8'):