Duma,

Select the range of cells, type the formula

=$A$1

(but with the cell address of the specific cell) and press Ctrl-Enter.

Or, type = and then select the specific cell and press Ctrl-Enter.  This is the better way if the
cell is on another sheet.

HTH,
Bernie
MS Excel MVP

Do you mean you want to perform some math operation on all the cells when you
input a number into one specific cell?

Assume number is entered in A1.

Assume range is B1:B100

In C1 enter  =B1*$A$1  which will multiply by the number in A1

Double-click on fill handle of C1 to copy down.

Another method is to enter a number in an unused cell.

Copy that cell.

Select the range to change and Paste Special>Multiply>OK>Esc

Change the number and do it again.

Gord Dibben  MS Excel MVP