Forumla HELP! Check boxes then counting £ values in columns

Hello community



This is my first post, struggling to achieve a formula command. can you help?



I have several columns, one being a check box column named "Payment"



When one or more of the rows is checked within this "Payment" column, I then need the system to calculate the £value across three other columns, names "30 days" "60 days" and "90 days" only when checked

(currently have inputted rows 1 to 15, this fluctuates dependant on business debtors, only a select number shown below for ref:







Below the rows above I have a formula section which feeds a dashboard:









I need the Total cash committed cell to count the  "30 days" "60 days" and "90 days" columns when "payment column" is checked positive



Any help appreciated, I've tried loads of different formulas and not having much look.  



Regards

Stuart