Power on, diodes on for 4 seconds?

Hi !

I have an idea, where I need a circuit, which can do the following:

**broken link removed**

There is a constant 12v power input connected to A (in the picture)

Then I need to have power to the diodes (1 and 2) for about 4 seconds, then they shall be "turned" off

There will be a constant 12v power to A..

And the next time 12v "hits" connection A the process needs to be restarted... Diodes shall be "turned" on for 4 seconds, and then "turn" off

How can this be done?

If it's possible I need a complete "recipe" beacuse, im a complete newbie at this

And sorry on my semi bad english.. Hope you guys can understand what I mean!

JitHstr,
"power to the diodes" in connection with your drawing doesn't make sense.
You say: "There will be a constant 12v power to A.." then you say: "And the next time 12v "hits" connection A..."
I think it would help to explain exactly what you are trying to do...the project not the solution.

Ken