Hola!! :
Código HTML:
Ver original<script type="text/javascript">
function setable(){
var button1 = document.getElementById('boton1');
var button2 = document.getElementById('boton2');
var button3 = document.getElementById('boton3');
if(button1.disabled == false){
button1.disabled = true;
button2.disabled = false;
}else if(button2.disabled == false){
button2.disabled = true;
button3.disabled = false;
} else if(button3.disabled == false){
button1.disabled = false;
button3.disabled = true;
}
}
<input type="button" id="boton1" value="Boton 1" onclick="setable()"/> <input type="button" id="boton2" value="Boton 2" disabled onclick="setable()"/> <input type="button" id="boton3" value="Boton 3" disabled onclick="setable()"/>