Value of first day of current month (except zero)-CodePudding

I need a way to get the value on column B that corresponds to the 1st day of the present month like so:

Table A
 --------------------- ------ 
|        ColA         | ColB |
 --------------------- ------ 
| 28/10/2012 00:19:01 |   42 |
| 29/10/2012 00:29:01 |  100 |
| 30/10/2012 00:39:01 |   23 |
| 31/10/2012 00:29:01 |    1 |
| 1/11/2012 00:19:01  |   24 |<---
| 2/11/2012 00:19:01  |    4 |
| 3/11/2012 00:19:01  |    2 |
 --------------------- ------ 

Table B
 --------------------- ------ 
|        ColA         | ColB |
 --------------------- ------ 
| 28/11/2012 00:19:01 |   67 |
| 29/11/2012 00:29:01 |    2 |
| 30/11/2012 00:39:01 |   63 |
| 31/11/2012 00:29:01 |    5 |
| 1/12/2012 00:19:01  |   69 |<---
| 2/12/2012 00:19:01  |   42 |
| 3/12/2012 00:19:01  |    6 |
 --------------------- ------ 

Table C
 --------------------- ------ 
|        ColA         | ColB |
 --------------------- ------ 
| 28/11/2012 00:19:01 |   11 |
| 29/11/2012 00:29:01 |   12 |
| 30/11/2012 00:39:01 |    3 |
| 31/11/2012 00:29:01 |   20 |
| 1/12/2012 00:19:01  |    0 |
| 2/12/2012 00:19:01  |   71 |<---
| 3/12/2012 00:19:01  |   21 |
 --------------------- ------

So I need to be able to have a formula that I can use in a cell anywhere on my sheet that gets me that "24" in Table A. In other words, it would always get me the value corresponding to the first day of the current month.

Then when the month is over and the next month starts, the same formula will get me the value on column B corresponding to the 1st day of the present month again, in Table B that would be "69".

Now one thing I'd like to add is, if the value on column B corresponding to the 1st day of the month is equal to "0" then the formula will search for the next cell/day until if finds a value greater than "0", and it outputs that one. See Table C. In this example it would be "71".

Is this possible? I imagine so I just can't figure out how to go about doing it.

Dummy file: