diff --git a/rowers/templates/summary_edit.html b/rowers/templates/summary_edit.html
index 93e1d89a..08322e00 100644
--- a/rowers/templates/summary_edit.html
+++ b/rowers/templates/summary_edit.html
@@ -83,7 +83,7 @@
 <td>8 times 500m with 3 minutes 30 seconds rest</td>
 </tr>
 <tr>
-<td>4x(500m+500m)/5min</td><td>4 times 1km, but each km is reported as two 500m intervals without rest</td>
+<td>4x((500m+500m)/5min)</td><td>4 times 1km, but each km is reported as two 500m intervals without rest. Note the nested parentheses.</td>
 </tr>
 <tr>
 <td>2x500m/500m</td><td>A 2k rowed as 500m "on", 500m "off"</td>
diff --git a/rowers/views.py b/rowers/views.py
index 3805e49a..3143e41a 100644
--- a/rowers/views.py
+++ b/rowers/views.py
@@ -19,6 +19,7 @@ from django.db import IntegrityError, transaction
 from django.views.decorators.csrf import csrf_exempt
 from matplotlib.backends.backend_agg import FigureCanvas
 import gc
+from pyparsing import ParseException
 
 from django.shortcuts import render
 from django.http import (
@@ -10926,8 +10927,8 @@ def workout_summary_edit_view(request,id,message="",successmessage=""
 	    s = cd["intervalstring"]
             try:
 	        rowdata.updateinterval_string(s)
-            except IndexError:
-                messages.error(request,'Interval string parse error')
+            except ParseException,err:
+                messages.error(request,'Parsing error in column '+str(err.col))
 	    intervalstats = rowdata.allstats()
 	    itime,idist,itype = rowdata.intervalstats_values()
 	    nrintervals = len(idist)
@@ -10936,7 +10937,11 @@ def workout_summary_edit_view(request,id,message="",successmessage=""
     # we are saving the results obtained from the mini language interpreter
     elif request.method == 'POST' and "savestringform" in request.POST:
 	s = request.POST["savestringform"]
-	rowdata.updateinterval_string(s)
+        try:
+	    rowdata.updateinterval_string(s)
+        except ParseException,err:
+            messages.error(request,'Parsing error in column '+str(err.col))
+            
 	intervalstats = rowdata.allstats()
 	itime,idist,itype = rowdata.intervalstats_values()
 	nrintervals = len(idist)