private void AddActionArgument()
		{
			string error;

			try
			{
				ActionArgument actionArg = new ActionArgument();
				actionArg.Name = txtName.Text;
				actionArg.Expression = BuildExpression();

				if (actionArg.IsValid())
				{
					actionArgs.Add(actionArg);
					RefreshActionArguments();

					txtName.Text = string.Empty;
					cbTarget.Text = string.Empty;
					cbPropertyOrValue.Text = string.Empty;
					ckIgnoreErrors.Checked = false;

					return;
				}
				else
				{
					error = actionArg.Error;
				}
			}
			catch(Exception e)
			{
				error = e.Message;
			}

			MessageBox.Show(error, "Add Action Argument",
			                MessageBoxButtons.OK, MessageBoxIcon.Error);
		}