A helper class that lets you draw a float field with more control. You can define a rect where the value is drawn/set and another rect where you can drag to scroll the value.

CustomFloatField.cs

using System;
using System.Reflection;
using UnityEngine;
using UnityEditor;

public static class CustomFloatField
{
	private static readonly int Hint = "EditorTextField".GetHashCode ();
	private static readonly Type EditorGUIType = typeof (EditorGUI);
	private static readonly Type RecycledTextEditorType = Assembly.GetAssembly (EditorGUIType).GetType ("UnityEditor.EditorGUI+RecycledTextEditor");
	private static readonly Type[] ArgumentTypes =
	{
		RecycledTextEditorType,
		typeof (Rect),
		typeof (Rect),
		typeof (int),
		typeof (float),
		typeof (string),
		typeof (GUIStyle),
		typeof (bool)
	};

	private static readonly MethodInfo DoFloatFieldMethodInfo = EditorGUIType.GetMethod ("DoFloatField", BindingFlags.NonPublic | BindingFlags.Static, null, ArgumentTypes, null);
	private static readonly FieldInfo FieldInfo = EditorGUIType.GetField ("s_RecycledEditor", BindingFlags.NonPublic | BindingFlags.Static);
	private static readonly object RecycledEditor = FieldInfo.GetValue (null);

	public static float Draw (Rect draw, Rect drag, float value, GUIStyle style)
	{
		var controlID = GUIUtility.GetControlID (Hint, FocusType.Keyboard, draw);
		var parameters = new object[] { RecycledEditor, draw, drag, controlID, value, "g7", style, true };

		return (float)DoFloatFieldMethodInfo.Invoke (null, parameters);
	}
}