I am trying to find a function or any other means to add up a row of numbers. The example is:

Week numbers on row 2
Value on row 3
Cell A1 has current week number

What function will look at cell A1 and return the total of the values in row 3 that have a week number of cell 1 or less.

Example :
Type 11 into current week cell at A1
Total returns the total of the value in row 3 that are against weeks 1 to 11.

I hope that's clear enough. I have tried SUMIF but cannot get the =< to work within the function.