I have a set of source columns named as "January, February, through December " and these values contain numeric values. At the beginning of the year, only the values for January have been filled out. At the beginning of each month, the values for that month's column will be filled up. Is there a function to set the default value of the rest of the months values to the last non null value?

For e.g., In January, I want to default the rest of the months values to the January values. In February, March through December should have the February values.