Can someone help , i will try to explain what i need as simply as possible.

I have a worksheet with multiple columns with each different record being entered on a new row within the worksheet.
I.e.
Column A - Room Name
Column B - Room Length
Column C - Room Width
Column D - Room Area (auto calculated using =B*C)

What i need is for the auto calculated formula to be used all the way down the column i.e. each row has the same formula to work out the row entered Length and Width

Problem is , when the rows have nothing entered in them , i.e. the user hasnt used the particular row , column D formula gives the error #DIV/0! when using a complex formula or the value 0.00 when using a simple formula like B*C. (I take it that Excel thinks that a blank cell has a value of 0.00)

Basically what i need to know is , if it possible to "activate" the formulas ONLY when the data that it needs has been entered . i.e. if no B or C field has been entered then the formula in field D is not activated and the cell is left blank.

If you are still with me and you know the answer then thank you for any help you can give.

Ray