Level of Effort (LOE) for Cost Summation

Hi

I am using P6, i have following problem

I have huge project with many activities, i want to add up duration of few consectivite activities , I have defined a dummy activity , assigned it a Level of effort activity type (LOE) , and assigned SS to Predessor and FF to successor ,

Now this dummy activity is summing up the duration , its fine , but its not summing up the budgeted costs . Its showing 0 cost.

Why is it soo...??????

Kindly help.