Changing existing sketch dimension with macro

Hi,

I have an application where I need to change a dimension in an existing sketch on several parts. The dimension is always D2@Sketch14 which controls a diameter.
I was wondering if anyone could make me a quick macro that will open all files in a specific folder, change the dimension, save and close the file. Or at least point me in the right direction, as I have little experience with creating visual basic macros!

Many thanks!

Kieran

SolidworksParts And Features