Any way to remove the number of points based on numbers selected in select list

Hello Sir,
I want to remove userpoint from a user based on the number selects when user creates the node. My work is based on credits. I want to grant userpoint based on credits which is defined in attributes. And when user creates the node there is option field in that time where 4 option '25,50,75,100' jobs are there. If user selects 25 then 1 userpoint will removed from total.for 50 the points will be removed are 2. Please help me.