Hi @R-b580 welcome to the community!
From what you are describing, it sounds like what would resolve this for you is leveraging the 'Run the step for these rows' run option
Here is a screenshot of my 'Sample_Table' where I want to insert a random number for any row in column2 that is blank.
In my app I created a button with an 'overwrite' automation and then specified this in the 'Run the step for these rows'
What this is saying is that for any row where 'Column2' is blank it will run this automation.
Then I specified to take date from =RAND() and write to =Sample_Table[Column2]
As a result what will happen on a button click is that the automation will look at each row that matches my run option and then individually for each row will take =RAND() and write to my column named 'Column2'. This leads to each row receiving it's own random number.
Hope this helps! Let us know if you have any further questions