I have a formula that references several other cells and calculates an average value while it weights each cells value by an incremental X value.

=-1*((1*K239)+(2*K238)+(3*K237)+(4*K236)+(5*K235)+(6*K234)+(7*K233)+(8*K232)+(9*K231)+(10*K230))/SUM(K230:K239)

I would like to be able to add a slider to the sheet that would enable me to adjust the numbere of cells included in the calculation. Each cell that was added would need to incremented by the x factor. As in the above formula it also must capture the added cells to be included for the divisor, in the above example /Sum(K230:D239).

Appriciate any and all ideas.

Michael