Goal Seek or Solve entire column automatically whenever value in respective row changes

[BKGLTS]

Hello,

I need help with the following please.

I need Goal Seek (or similar function) to determine what number A2 needs to be in order for B2 to equal 0.
I need this to happen for all cells in column A rows 2 through 501.
Ideally the goal seek in column A would only happen on the row that a change occurred so not all rows are being recalculated when nothing changed in their respective rows.

Sounds like this may be a VBA code solution.

Thank you,
B