Copying formulas where source "jumps" in bigger gaps than target.

Hmm.. maybe a akward headline... But I want to do the following;

sheet1 contains info ranging like A4, A8, A12, A16.... A200

sheet2 shall display the value of the mentioned cells from sheet1, but in the following place D2, D4, D6, D8, D10.... D100

So if I copy the formula from cell Sheet2.D2 to Sheet2.D4 it says =Sheet1.A6 since I only moved two steps down in Sheet2 but wanted to go 4 in Sheet1. I want it to edit the "steps" taken when copying, possible??

It seems so basic but I just can't figure out how to do it....

Please help, or I will have manually edit 100+ cells....

/Johan