I'm looking for a way to get this formula to continue on changing value every
10 numbers but only increasing 2 numbers in the result.

=IF(C7<=19,"4",IF(C7<=29,"6",IF(C7<=39,"8",IF(C7<= 49,"10",IF(C7<=59,"12",IF(C7<=69,"14",IF(C7<=79,"1 6",IF(C7<=89,"18",))))))))

I need an expert in writing code