How to overlay binary image on a gray scale image

Hi.. I want to overlay a binary image on a gray scale image using imoverlay function in MATLAB 7.2 (R2006a). But i am currently working in MATLAB 2009a.. I can't use that function.Instead i have used transparency method...After that i need to do morphological reconstruction of the image using imreconstruct function ..When i used this I got error like," both marker and mask image need to be same size,pixels in marker should be greater than or equal to mask". Can anyone help me to use imoverlay and imreconstruct function...Thanks in advance......