Subtract 20 repeatedly from an original value until the value reaches zero

I am a professed excel noob and so I need help writing this function. I need to write a function where a column of values will subtract from an original value until the value reaches zero.

If my original value is 125, I need the following table to look like this

B1 20
B2 20
B3 20
B4 20
B5 20
B6 20
B7 5

I need the function to be generic so that I can start with any original value and the function will show 20 in the column cells until the value reaches less than 20 in the final cell.

hope this makes sense.