How do I add or sum until?

iwaddo Since it's for personal use, you could try the following formula in cell E3 to return the desired results:

=MAP(A3:A8, B3:B8, C3:C8, LAMBDA(seq,vol,cos, LET(
    by_arr, DROP(A2:seq, -1),
    total_vol, SCAN(0, SORTBY(DROP(B2:vol, -1), by_arr, -1), LAMBDA(a,v, a + v)),
    unit_cost, SORTBY(DROP(C2:cos, -1), by_arr, -1),
    used_vol, SORT(VSTACK(vol, total_vol)) - VSTACK(0, total_vol),
    SUMPRODUCT(DROP(used_vol, -1), unit_cost)))
)

Example Results

However, I should point out that the logic used here is flawed (it's not an accurate LIFO method). As you can see in your original screenshot, it will "double dip" from the wrong transaction line(s) whenever the volume purchased is greater than the previous row(s):

Original Example

Alternatively, you could use a weighted average method, which is a common accounting practice:

=MAP(B3:B8, D3:D8, LAMBDA(vol,cos, SUM(D2:cos) / SUM(B2:vol) * vol))

Please see the attached workbook, if needed...