How to select and repalce duplicates with blanks from one column based on duplicates in another column?

[#1]

Lets say I have two column data. First column with English alphabets appearing sequentially in Capital case (A--> Z), with each alphabet appearing say 7 times before the next. The second column has the same repetition but in small case (a--z). I want keep only one entry for the small case letter in the second column for each Capital letter in column 1. Rest of the entries in second column I want to set as blanks. 

(In my actual data the repetition is not fixed to 7 times and is variable. Also, my data is numerical and not character)

How to achieve this via JSL?

"Column 2 result" is what I want in "Column 2"

[#2]

If your data is numeric how it goes from capital letters to non-capital ones? And is the repetition same in same data set or can it change between the values?

[#3 · Accepted solution]

If I am understanding what you want, I believe the solution is 

names default to here(1);
dt=current data table();
dt << new column("result",
	formula(
		if(row()==1 | :column 1 != lag(:column 1), :column 2)
	)
);