Short answer

Use an open ended reference.

Explanation

A range reference has two parts, the address of the start cell and the address of the end cell. On the A1 notation usually the cell address includes a letter to specify the column and number to specify the row.

  • A:A specifies the whole column
  • A2:A specifies that the start cell is A2 and that the last cell is the last one of the A column.

For the specific case in the question, instead of

SUM(A10:A500)

try

SUM(A10:A)