Google sheets: sum up column until dropdown is true

[ddnndd1234]

in column A i have a list of numbers, in column c there is a drop down of true and false. If the cell is true I would like the numbers at that cell and above to add up until the previous true cell in column B. The sum will be in column b beside the "true" cell. If false column stays blank

Thanks

 

[ddnndd1234]

=IF(C2,SUM(A$2:A2)-SUM(B$1:B1),"")

Thanks to Kaper