Why does the formula move when I move the column

Hi
I have a spreadsheet that adds the numbers in a column on sheet 2 eg C3 to C43 and puts the result in a cell on sheet1
I now want to insert a new column in sheet 2 column C so that I can add more numbers and get a new result on sheet1
But the formula seems to stay with the original column so that the cell in sheet1 is now looking at D3 to D43
How can I lock the formula on column C
Many Thanks

You could do it this way

=SUM(INDEX(Sheet2!A3:Z43,0,3))

Thanks but it doesn't seem to work
I typed your formula into the cell on Sheet1 then inserted a new column C in Sheet2 but it did not recalculate the figures
But excel changed the formula by itself to

=SUM(INDEX(Sheet2!A3:AA43,0,3))

The formula you have will sum all the rows (that's what the 0 signifies) of the 3rd column (that's what the 3 before the 2 closing brackets signifies) of the specified index (which is columns A to AA) - that would be the new column C.

What result did you get when you inserted the new column? It should be 0 until you put values into that new column.

Thank You Cutter
It was my fault it didn't work the first time
Thanks for your help

You're welcome - and thanks for the 'star tap'.

Enjoy the Olympics! I hope you get sick of hearing the Canadian anthem.