Is it possible to apply column formula only for BLANK values at the same column?!?

[MartinS_CZ]

Hello guys,

I have maybe a bit weird questions – is it possible in DAX (or PQ) make a column formula, which is applied only for BLANK cells at the same column? 

I need to compare todays date with other column date, and do it on daily basis then, so first day after this comparison some rows to be filled as TRUE (today = date in other column), and next day it is done again, with "today of next day" date comparison, but NOT to overwrite TRUE values already filled from the day before. 

And so on, day by day just compare it and fill the rest BLANK cells only, but keep the ones already filled with TRUE from previous days.

Kind of “freezeing” already existing values, and apply the formula only for the blank cells.

Something like this (just to understand my thoughts): 

DateComparison =
(IF (DateComparison) ISBLANK,
(IF (DateComparison) = (TODAY),
“TRUE”),
else,
””
))

Thanks a lot Martin

[amitchandak]

@MartinS_CZ , Based on what I got.

If you want to replace , then use replace in power Query and replace null  with some value 

Power Query Replace Value: https://youtu.be/hkZhZbR7Kmk

In dax you can have new column like

if(isblank([COlumn]), "A", blank())

Keep the data type same( in then and else )  or use blank