copy information linked to next colum

I have a table that looks like this:

Colum a Colum b Column c
data1 data x data a Data b
data a1 Data b
data a2 data b
Blank raw
Data2 data y data c data d
data c1 data d
data c2 data d
data c3 datad
etc
I want to copy data on colum a (data1 and data x) to the next two rows (left
of data a, a1 and a2) and do the same on the same colum a but copy data2 and
paste on the next raw (data c1, c2, c3)I have a table for more that 60,000
raws and need to do this several times, information by blocks (blank raws
betwen them)