Starting a process when another one is finished as seen by a row in a table updated

[SasStatistics]

In my company, I run a process once a month after another one is finished. To know that it is finished, I manually look at the following table (it has about 100 more rows in reality): 

Latest date for finishing the process	Date when the process was finished	Process has begun
31-jan-22	05-jan-22	1
28-feb-22	04-feb-22	1
31-mar-22	03-mar-22	1
30-apr-22	05-apr-22	1
31-maj-22	.	0
30-jun-22	.	0
31-jul-22	.	0
31-aug-22	.	0
30-sep-22	.	0
31-okt-22	.	0
30-nov-22	.	0
31-dec-22	.	0
31-jan-23	.	0
28-feb-23	.	0
31-mar-23	.	0
30-apr-23	.	0

Assuming we are currently standing in april-2022. 

Since there is a date (05-apr-22) in the column "Date when the process was finished" I know that the process has been finished and I can run my process. An extra sanity check is that the column "Process has begun" should have a 1 in the row for the relevant month. So if there is a date in the relevant row I should run my process. BUT, this should only be done once every month.

Next month, in May I will every day look when the middle column gets an date: 

31-maj-22

.

0

when it has I will run my process. 

Obviously, this is a manual process that can be automatized and my goal is to set up an SAS Program that perfroms the test (say once day) which will be done automatically by scheduling the SAS program. Any advice how I could write a SAS program to perform the desired test? I also want to emphasize, that if we are standing in april 2022 for instance: 

30-apr-22

05-apr-22

1

then the 05-apr-22 I could run my process, but I should not run it anymore that month, so I should continue to next month and check when there comes an date. 
I also know that in the column "Date when the process was finished", when there is something filled up it should be the same month and year as in the column: Latest date for finishing the process. Else something is wrong. 

I hope it is clear what I mean, appreciate your help! 

[ChrisNZ]

The easiest way is:

1- In the first process, once everything is OK, write out a text file somewhere.

2- The second process can start at the same time, and checks every few minutes that the file exists.

  Once the file is found, exit the waiting loop and run the rest of the code.

[SasStatistics]

1. Unfortunately not possible since it is a process I have no control over and cannot affect.
2. This as far as I can see could lead to my process beeing run several times a month, it should only be run once.

[Sajid01]

In the corporate environment schedulers (Autosys, Contol-M etc) take care of this. Starting the second job after the first has finished.
If that is not possible in your case and if you are on a  Unix/Linux environment you can write a batch script that can do this job.
If either of the above two are not possible then the suggestion by @ChrisNZ is your best choice..

[ChrisNZ]

 Unfortunately not possible since it is a process I have no control over and cannot affect.

The next best method then, if your scheduler can't link jobs, could be to check the file:
- Check the sas date set's (file *.sas7bdat) update date.
- It it has been updated, open it and validate the data.

You need these 2 steps as doing only step 2 could lock the data set just when job1 wants to upate it.

This as far as I can see could lead to my process beeing run several times a month

I don't see why.