This is what I have:
Columns A/B/C/D/...
Last Name/First Name/Social Security Number/Time Worked/...

Some employees have multiple entries to track multiple times they have
worked for the firm. I have a summary entry for the total time worked, but I
entered it as follows.

[blank]/[blank]/[blank]/100 (summation of time worked listed below)
Doe/John/xxx-xx-xxxx/50
Doe/John/xxx-xx-xxxx/50

I need the [blank] entries to be filled in by the proceeding rows. In the
end, I want every row to have Last Name/First Name/SSN. Some of the
employees have only one row, or entry. In that case, I want to leave the
cell unchanged. The formula I've tried using is:
=IF(AND(ISBLANK(A2),(ISBLANK(B2),iSBLANK(C2)),A3,A 2)

If you need more explanation or clarity of information, let me know. Any
input is appreciated!