Macro to copy row into next blank row with condition

[Estrella]

[TABLE="width: 195"]
<tbody>[TR]
[TD="class: xl63, width: 65"]header[/TD]
[TD="class: xl63, width: 65"]test[/TD]
[TD="class: xl63, width: 65"]details[/TD]
[/TR]
[TR]
[TD]a[/TD]
[TD]alpha[/TD]
[TD="align: right"]10[/TD]
[/TR]
[TR]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD]a[/TD]
[TD]beta[/TD]
[TD="align: right"]400[/TD]
[/TR]
[TR]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD]b[/TD]
[TD]zoo[/TD]
[TD="align: right"]32[/TD]
[/TR]
[TR]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD]b[/TD]
[TD]gamma[/TD]
[TD="align: right"]500[/TD]
[/TR]
</tbody>[/TABLE]


Hello there,

I have this spreadsheet starting in A1 with a header row. Then I have another row in row 2 ( a-alpha-10 in my example ), then one empty row every two rows. ( so row a-beta-400 is row 4). The last row is not known but the number of rows will never be more than 200 rows.

I need to copy row 2 into row 3, them copy row 4 into row 5, then row 6 into row 7 etc etc.
Additionally I need a condition to change the value of cell A. For example if value in cell A2 is "a" I need the value to be changed into "z" when copying it into A3. If the value in A2 is "z" I need the value copied in A3 to become "a". These will be the only 2 values possible.

I have failed to make this think work so far! Any hints? Many thanks