start = datenum(2012, 3, 31, 0, 0, 0)
Next, use datenum again to define the interval of 7 days:
offset = datenum(0, 0, 7, 0, 0, 0);
Finally, make a 100-element vector by multiplying the numbers 0 through 99 by the offset and adding them to the start date:
vec = start + (0:99)*offset;
You can verify the results by converting the serial date numbers in vec back to strings:
datestr(vec)
