How can I make a custom Time Range Selector (with sliders)?

I’m trying to use GUI.DrawTexture to create a custom progress bar type object within OnInspectorGUI. Despite the fact that I haven’t been able to get it to work outside of OnGUI, I also haven’t had luck creating what I want. Basically, I have two sliders that control the range you select. The first would select the opening value of the range, and the second selects the end value. There would then be a texture drawn in between the two that updates with the sliders as you move them. Outside of the range, the texture would be different on each end. Currently, I only have a custom progress bar that fills in from one side working, based on answers from other questions. Is a selector like this possible to create with Unity’s API?

Here’s my code so far:

 var startSliderValue : float = 0.0;
 var endSliderValue : float = 1.0;
 var pos : Vector2 = new Vector2(20,40);
 var size : Vector2 = new Vector2(200,20);
 var progressBarEmpty : Texture2D;
 var progressBarFull : Texture2D;

 function Start() {
   progressBarEmpty = Resources.Load("white-texture-large");
   progressBarFull = Resources.Load("Black");
 }

 function OnGUI() {  //Ideally, this is OnInspectorGUI in an Editor class
   GUI.DrawTexture(Rect(pos.x, pos.y, size.x, size.y), progressBarEmpty);
   GUI.BeginGroup(new Rect (pos.x, pos.y, size.x * Mathf.Clamp01(startSliderValue), size.y));
   GUI.DrawTexture(new Rect(0, 0, size.x, size.y), progressBarFull);
   GUI.EndGroup();  
 }

The sliders are in a different script within the Inspector.

To do this, I ended up using EditorGUI.DrawPreviewTexture instead of GUI.DrawTexture. I also used a MinMaxSlider from EditorGUILayout to specify a time range. DrawPreviewTexture draws a dynamic color bar underneath to show where previous time ranges were saved (reading from XML). Since DrawPreviewTexture requires a texture to show, I just initialize my own color textures based on how many time ranges I have with the following function:

/// <summary>
/// Create a texture with a unique color based off of the current
/// _numTimeRanges.
/// </summary>
function createNewTexture(_numTimeRanges : int)
{
  var texture : Texture2D = new Texture2D(128, 128);

  for (var y : int = 0; y < texture.height; y++) {
    for (var x : int = 0; x < texture.width; x++) {
      var color : Color;

      if (_numTimeRanges == 0) {
      	color = Color.white;
      }
      else if (_numTimeRanges % 4 == 1) {
      	color = Color.red;
      }
      else if (_numTimeRanges % 4 == 2) {
      	color = Color.blue;
      }
      else if (_numTimeRanges % 4 == 3) {
      	color = Color.yellow;
      }
      else if (_numTimeRanges % 4 == 4) {
        color = Color.black;
      }

      texture.SetPixel(x, y, color);
    }
  }

  texture.Apply();
}