Is it possible to get Botox to crows feet only?

Anti-wrinkle injections are most commonly used for treatment of frowns, forehead lines, and crows feet (at the sides of the eyes).  
You most certainly can treat only one area or all areas. 

Yes, it is certainly possible to have Botox only applied to the crows feet wrinkles around the eyes. Doing so will not have any adverse effects on how you appear. So if you choose to not address the forehead area, that is completely fine. The main thing to remember when making decisions on a Botox treatment is to choose a skilled and highly experienced provider. Ideally, your doctor should have board certification in plastic surgery or dermatology. A high-level expertise on facial anatomy is a must-have since Botox works at the level of the nerves and muscles. 
For addressing crows feet wrinkles (and any other region), the provider must know exactly where to place the injection, instead of relying on a standard facial map. Injecting too low for the crows feet area may affect the cheek muscles, for example. They must also have a clear idea on what results their dosage and placement decisions will have for specific patients. Hope this helps. (159 words) 

Of course it is perfectly fine to do just the crow's feet and many of our patients do just that. It is a distinct area from the forehead and shouldn't interact. Be sure to see an experienced injector to get Botox done.