Need Strikethrough To Subtract Value From Subtotal

I have a situation where Cell A1 displays the subtotal of Cells A2 through A10:

Cell A1=100
Cell A2=20
Cell A3=30
Cell A4=40
Cell A10=10

I need the subtotal cell to subtract any of the values that get formatted with the Strikethrough feature:

Cell A1=60
Cell A2=20
Cell A3=30
Cell A4=40 (this value receiving the strikethrough)
Cell A10=10

How can this be done?