How to skip unselecting pictures?

[coody]

I want to select most of pictures. So I first clicked on Ctrl + A to select all 100 pictures. Now I want to unselect several pictures, for example, #20, #30, #70 and so on without losing the other pictures. Does anyone know it?

[RowMan]

Assuming you're using Windows, you just hold down Ctrl and click on the pictures you want to un-select.