diff --git a/lasp/lasp_common.py b/lasp/lasp_common.py
index 2bb9e74..421c9dd 100644
--- a/lasp/lasp_common.py
+++ b/lasp/lasp_common.py
@@ -96,6 +96,13 @@ class SIQtys:
     def getCurrent(cb):
         return SIQtys.types[cb.currentIndex()]
 
+    @staticmethod
+    def getIndex(qty):
+        for i, qtyi in enumerate(SIQtys.types):
+            if qtyi == qty:
+                return i
+        return -1
+
 @dataclass
 class CalSetting:
     name: str