Index: /trunk/Ohana/src/opihi/cmd.basic/run_for.c
===================================================================
--- /trunk/Ohana/src/opihi/cmd.basic/run_for.c	(revision 27797)
+++ /trunk/Ohana/src/opihi/cmd.basic/run_for.c	(revision 27798)
@@ -7,5 +7,5 @@
   int ThisList, depth, i, done, status, found, NLINES, j;
   double start, end, delta;
-  char *input;
+  char *input, *endptr;
   double value, sign;
   Macro loop;
@@ -16,8 +16,24 @@
   }
 
-  start = atof (argv[2]);
-  end   = atof (argv[3]);
+  start = strtod (argv[2], &endptr);
+  if (*endptr) {
+    gprint (GP_ERR, "for loop starting value must be numerical (%s)\n", argv[2]);
+    return (FALSE);
+  }
+
+  end = strtod (argv[3], &endptr);
+  if (*endptr) {
+    gprint (GP_ERR, "for loop ending value must be numerical (%s)\n", argv[3]);
+    return (FALSE);
+  }
+
   delta = 1.0;
-  if (argc == 5) delta = atof (argv[4]);
+  if (argc == 5) { 
+    delta = strtod (argv[4], &endptr);
+    if (*endptr) {
+      gprint (GP_ERR, "for loop delta value must be numerical (%s)\n", argv[4]);
+      return (FALSE);
+    }
+  }
   sign = SIGN(delta);