diff --git a/gui/graphFrame/input.py b/gui/graphFrame/input.py
new file mode 100644
index 000000000..cc73417ce
--- /dev/null
+++ b/gui/graphFrame/input.py
@@ -0,0 +1,98 @@
+# =============================================================================
+# Copyright (C) 2010 Diego Duclos
+#
+# This file is part of pyfa.
+#
+# pyfa is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# pyfa is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with pyfa.  If not, see <http://www.gnu.org/licenses/>.
+# =============================================================================
+
+
+import wx
+
+import re
+
+
+def valToStr(val):
+    if val is None:
+        return ''
+    if int(val) == val:
+        val = int(val)
+    return str(val)
+
+
+def strToFloat(val):
+    try:
+        return float(val)
+    except ValueError:
+        return None
+
+
+class ConstantBox(wx.TextCtrl):
+
+    def __init__(self, parent, initial):
+        super().__init__(parent, wx.ID_ANY, style=0)
+        self.Bind(wx.EVT_TEXT, self.OnText)
+        self._storedValue = ''
+        self.ChangeValue(valToStr(initial))
+
+
+    def ChangeValue(self, value):
+        self._storedValue = value
+        super().ChangeValue(value)
+
+    def OnText(self, event):
+        currentValue = self.GetValue()
+        if currentValue == self._storedValue:
+            event.Skip()
+            return
+        if currentValue == '' or re.match('^\d*\.?\d*$', currentValue):
+            self._storedValue = currentValue
+            event.Skip()
+        else:
+            self.ChangeValue(self._storedValue)
+
+    def GetValueFloat(self):
+        return strToFloat(self.GetValue())
+
+
+class RangeBox(wx.TextCtrl):
+
+    def __init__(self, parent, initialLow, initialHigh):
+        super().__init__(parent, wx.ID_ANY, style=0)
+        self.Bind(wx.EVT_TEXT, self.OnText)
+        self._storedValue = ''
+        self.ChangeValue('{}-{}'.format(valToStr(initialLow), valToStr(initialHigh)))
+
+    def ChangeValue(self, value):
+        self._storedValue = value
+        super().ChangeValue(value)
+
+    def OnText(self, event):
+        currentValue = self.GetValue()
+        if currentValue == self._storedValue:
+            event.Skip()
+            return
+        if currentValue == '' or re.match('^\d*\.?\d*\-?\d*\.?\d*$', currentValue):
+            self._storedValue = currentValue
+            event.Skip()
+        else:
+            self.ChangeValue(self._storedValue)
+
+    def GetValueRange(self):
+        parts = self.GetValue().split('-')
+        if len(parts) == 1:
+            val = strToFloat(parts)
+            return (val, val)
+        else:
+            return (strToFloat(parts[0]), strToFloat(parts[1]))
diff --git a/gui/graphFrame/panel.py b/gui/graphFrame/panel.py
index 1ffdf5b7c..504630ea0 100644
--- a/gui/graphFrame/panel.py
+++ b/gui/graphFrame/panel.py
@@ -23,6 +23,7 @@ import wx
 
 from gui.bitmap_loader import BitmapLoader
 from service.fit import Fit
+from .input import ConstantBox, RangeBox
 from .lists import FitList, TargetList
 from .vector import VectorPicker
 
@@ -143,18 +144,14 @@ class GraphControlPanel(wx.Panel):
         self.inputsSizer.Clear()
         self.inputs.clear()
 
-        def addInputField(inputDef, handledHandles):
+        def addInputField(inputDef, handledHandles, mainInput=False):
             handledHandles.add(inputDef.handle)
             fieldSizer = wx.BoxSizer(wx.HORIZONTAL)
-            fieldTextBox = wx.TextCtrl(self, wx.ID_ANY, style=0)
+            if mainInput:
+                fieldTextBox = RangeBox(self, *inputDef.defaultRange)
+            else:
+                fieldTextBox = ConstantBox(self, inputDef.defaultValue)
             fieldTextBox.Bind(wx.EVT_TEXT, self.OnFieldChanged)
-            if inputDef.defaultValue is not None:
-                inputDefault = inputDef.defaultValue
-                if not isinstance(inputDefault, str):
-                    inputDefault = ('%f' % inputDefault).rstrip('0')
-                    if inputDefault[-1:] == '.':
-                        inputDefault += '0'
-                fieldTextBox.ChangeValue(inputDefault)
             fieldSizer.Add(fieldTextBox, 0, wx.EXPAND | wx.ALIGN_CENTER_VERTICAL | wx.RIGHT, 5)
             fieldIcon = None
             if inputDef.iconID is not None:
@@ -182,7 +179,7 @@ class GraphControlPanel(wx.Panel):
             handledHandles.add(tgtVectorDef.angleHandle)
         selectedX = view.xDefMap[self.xType]
         # Always add main input
-        addInputField(view.inputMap[selectedX.mainInput], handledHandles)
+        addInputField(view.inputMap[selectedX.mainInput], handledHandles, mainInput=True)
         for inputDef in view.inputs:
             if inputDef.mainOnly:
                 continue
@@ -217,8 +214,8 @@ class GraphControlPanel(wx.Panel):
 
     def OnDrawTimer(self, event):
         event.Skip()
-        self.graphFrame.clearCache()
-        self.graphFrame.draw()
+        # self.graphFrame.clearCache()
+        # self.graphFrame.draw()
 
     def getValues(self):
         values = {}