How do you select layers to exclude during selection. To exclude, use ! but not sure how to refer to a specific layer. Should it by !1, or !L1, etc? The best way to exclude use for layers is to "Lock" them. This will allow you to view the layers but you cannot select them. To lock layers, go to the Layers Table (menu: Setup | Layers Table...), and under the column Lock check the layers you wish to lock.
Note: You can also Lock layers (without using the Layers Table) by Right-Clicking your mouse over any layer in the Layer Control (located in the Design Navigator on the Left), and then check Lock.
To Unlock Layer(s), repeat the same steps above, except un-check the layer(s).