The week is an arbitrary unit of time. It doesn't matter.
Just take the total of amount of sust that you want to use in the cycle and divide it by the total number of shots.
eg. Suppose you want to take 500 mg a week for a 10 week cycle.
that would be 5000 mg over 70 days. since you want to shoot eod, you will need a total of 35 shots. divide the 5000 mg by the 35 shots and you get about 140 mg per shot. Since sust. 250 has 250 mg/ml you will need 0.56 ml in each shot. Since I rounded a little, I would just go with 0.6 ml for ease of measure.
Since 7 is an odd number, the days you inject will change, but it is pretty easy to remember if you didn't take an injection yesterday, then you need one today.