Simple function but..., variable + array

Hi
Today I have:

for (condition){
//Income
if (_global.chart_no==1){
current_value= _global.income_md;// _global.income_md is an array
}
//Costs
if (_global.chart_no==2){
current_value= _global.costs_md;// _global.costs_md is an array
}
//Profit
if (_global.chart_no==3){
current_value= _global.profit_md;// _global.profit_md is an array
}

}

In stead I would like something outside the for condition making it variable what array is to be selected:

work_with_this_alue=current_value + *;

How is the last line to be written in order to create this flexibility ?

Best regards