What if you set a class for all sibling containers (i.e. columns) and set:
DIV.myColumnClass:first-child {
padding: 0px 20px; /* left and right padding */
}
DIV.myColumnClass {
padding: 0px 20px 0px 0px; /* right padding */
}
DIV.myColumnClass:last-child {
padding: 0px;
}
It's somewhat different: the first column will have left and right padding, the other columns just the right one, the last one no left or right padding.