Using A:A with dynamic setting

Can we set up A:B used for Sumif/Vlookup such that it will only consider column upto where the data is available.

let's say, In the B column, there is blank data in Column 26,78,67,89,123,567 and the last data is in 670.

So, I only need to lookup data up to A1:B670 but it should be incorporated in A:B such that even if a new data is added in B671, it should be considered instead of manually changing.

The reason is I have data where A column is filled till A1500 with unique codes and name against them are updated periodically in Column B. I know that I can use iferror for this but can we do it without it?

I remember reading a comment where a user recommended using something like "." or other symbol in A:B such that it dynamically changes based on the last data but I'm not able to find it now.

Thanks.