How would i get this logic into a marco or formula?

if 'sheet1' a1 > 0 then a1 = 'sheet1' a1
then auto fill until sheet1 a* = 0
so it might look like

a1 = 'sheet1'a1
a2 = 'sheet1'a2
a3 = 'sheet1'a3
etc...
until 'sheet1' a* = 0

then when 'sheet1'a* = 0 a* = 'sheet2' a1
and then auto fill until sheet2 a* = 0
so it might look like:

a70 = 'sheet2'a1
a71 = 'sheet2'a2
a72= 'sheet2'a3
etc...
until 'sheet2' a* =0

the issue i am having is that i cant get the autofill to populate sheet2 at a1, it starts at maybe a76 or where ever the autofill from sheet1 stops.

so it looks like
a70='sheet2'a70
a72='sheet2"a71
a73='sheet3"a73
etc...
which are empty

so i would need excel to read all of sheet1 and then start at the top of sheet2 and populate that on a different sheet sheet3

thanks