Hello, I have a problem with my Dodge Grand Caravan. when I tried to lock it or open it using the one on door (driver side) is not working,

 

You probably have a broken lock actuator rod clip. Available from the dealer or the HELP section of autoparts store, $3-4 BUCKS.

If you pull the door panel, and look inside you may find a loose 1/2 rod that connects the key lock to the lock mechanism.
These aren't hard to replace. Push the clip into the mechanism, slide rod thru the hole and rotate the clip up onto the rod.

It's harder to explain than to just look at it.

DG

 

These lock assemblies are a unitized design and many times the whole unit has to be replaced. If it isn't obvoius that a link is loose, it may be the lock asm. They are very pricey new (about $75, but can be had at a pick & pull for $10. It is a very easy R&R if it comes to that