=SUMPRODUCT(ROW(A1:A7),A1:A7)

I notice that you are confused between rows and columns, Chris. A is a
column, not a row, and A3 is the 3rd row in that column.
--
David Biddulph

Chris wrote:
I have a fixed row of 7 cells, any one of which might contain a
number. the cell with the number is the relevant one and it will
determine my formula; i will want to multiply the cell value by a
number in another cel which is chosen according to the number of the
cell in the original row.
eg A1:A7- A3 contains 21
formula in A50 will wish to determine 21 x value of cell in column 3
of a range of columns because the number 21 is in cell 3 in the row.

I was planning to use V or HLookup I think but cant fathom how to get
the cell number form the original row.

TIA Chris