If your home was built with attentive care to preventing water intrusion via an exterior french drain system, you should not have an immediate or even a long term worry about water in the webs if your block.

However, tar foundation coating is not a water proofing compound, it is a vapor proofing compound and over time, if your french drain fails, you could have water penetration into your basement.

DryLok will serve as a water and vapor barrier but should not be used as your first line of defense in this regard.

Water and vapor proofing should always be done on the outside of the foundation, but it is not always practical or economical to do so. Especially after a home has been completed.

the house does have a french drain at the footer. i was told i could fill the block with expanding foam. this would insulate the wall and also help keep out moisture. has anyone had any experience with this? i am looking to make the basement as dry as possible before i finish it. i will be make part of it into a office and the rest of it a rec room. thanks

Expanding foam will insulate your walls but it is not a waterproofing or a vapor proofing material.

Foam actually has a high permeablity rating.
Permeability is the quality of a material to allow water or water vapor to pass.

The only way to prevent water from entering your blaock is to apply a specialty coating to the outside of the foundation or a rubber membrane around the outside of the foundation.

Homebild is right. The only way to "Waterproof a wall" is an exterior dig up. Foam injection in the wall will insulated but will not waterproof because you cannot completely fill the void of the wall. Closed cell urethane foam is zero perm but cannot be used as waterproofing in this case.
The other method is water management. This involves cutting the floor and installing a footer drain inside.

This will not keep the water out but offers a way to catch it before it causes you harm. Be aware of humidity levels before and after any work. It is possible to stop the water but increase the humidity. High humidity can lead to mold.

Hope this helps,

Keith