diff --git a/MathPad/MPExpression.h b/MathPad/MPExpression.h
index 556c8cf..ad83b88 100644
--- a/MathPad/MPExpression.h
+++ b/MathPad/MPExpression.h
@@ -603,6 +603,9 @@
 - (void)replaceElementsInIndexedRange:(NSRange)range
                          withElements:(NSArray *)elements;
 
+- (void)replaceSymbolsInRangePath:(MPRangePath *)rangePath
+                     withElements:(NSArray *)elements;
+
 
 /*!
     @method     appendElement:
diff --git a/MathPad/MPExpression.m b/MathPad/MPExpression.m
index 5d3ca5d..3ab7318 100644
--- a/MathPad/MPExpression.m
+++ b/MathPad/MPExpression.m
@@ -91,7 +91,9 @@
 
 @implementation MPExpression {
     NSUInteger _cachedLength;
+    
     NSRange _editedRange;
+    BOOL _didSplitStartOnEditing;
     BOOL _didSplitEndOnEditing;
     NSUInteger _replacementLength;
 }
@@ -144,15 +146,17 @@
                 [_elements replaceObjectsInRange:NSMakeRange(index, 2)
                                 withObjectsFromArray:@[new]];
                 NSUInteger maxReplacementIndex = _editedRange.location + _replacementLength;
-                if (index == _editedRange.location - 1) {
+                if (index == _editedRange.location-1 && !_didSplitStartOnEditing) {
                     --_editedRange.location;
                     ++_editedRange.length;
+                    if (index == maxReplacementIndex-1 && !_didSplitEndOnEditing) {
+                        ++_editedRange.length;
+                        ++_replacementLength;
+                    }
                 } else if (index >= _editedRange.location && index < maxReplacementIndex - 1) {
                     --_replacementLength;
-                } else if (index == maxReplacementIndex - 1) {
-                    if (!_didSplitEndOnEditing) {
-                        ++_editedRange.length;
-                    }
+                } else if (index == maxReplacementIndex-1 && !_didSplitEndOnEditing) {
+                    ++_editedRange.length;
                 }
                 --index;
             }
@@ -222,12 +226,28 @@
     _cachedLength = 0;
     
     NSUInteger editLocation = startIndex - (didSplitStart ? 1 : 0);
-    NSUInteger editLength = range.length > 0 ? (endIndex - startIndex) : 0;
+    NSUInteger editLength = endIndex - startIndex;
+    if (range.length == 0 && didSplitStart) {
+        editLength = 1;
+    }
+
     _editedRange = NSMakeRange(editLocation, editLength);
+    _didSplitStartOnEditing = didSplitStart;
     _didSplitEndOnEditing = didSplitEnd;
-    _replacementLength = elements.count + (didSplitStart ? 1 : 0) + (didSplitEnd ? 1 : 0);
-    
+    _replacementLength = elements.count;
+    if (didSplitStart) {
+        _replacementLength++;
+        if (range.length == 0) {
+            _replacementLength++;
+        }
+    }
+    if (didSplitEnd) {
+        _replacementLength++;
+    }
+
     [self fixElements];
+    [self.evaluator expressionDidChangeInRange:_editedRange
+                             replacementLength:_replacementLength];
     [self didChangeElementsInIndexedRangePath:[[MPRangePath alloc] initWithRange:_editedRange]
                      replacementLength:_replacementLength];
 }
@@ -546,6 +566,14 @@
                    withElements:elements];
 }
 
+- (void)replaceSymbolsInRangePath:(MPRangePath *)rangePath
+                     withElements:(NSArray *)elements
+{
+    MPExpression *targetExpression = [self elementAtIndexPath:[rangePath.location indexPathByRemovingLastIndex]];
+    [targetExpression replaceSymbolsInRange:rangePath.rangeAtLastIndex
+                               withElements:elements];
+}
+
 - (void)appendElement:(id<MPExpressionElement>)anElement
 {
     [self appendElements:@[anElement]];