cell references

[worc1152]

Does anyone know how to (if possible) either:
a) have a formula which includes references to cell formats rather than cell numbers... ie. i want it to add all numbers between 2 cells which are in bold:

row no. data (column A)

1 28

2 15

3 7

4 15

5 11

6 8

7 9

8 11

ie. i want it to add 15 & 7 and put the total in B4, and add 11 & 8 & 9 and put the total in B8... and i want to be able to copy the formula down the whole spreadsheet without changing the reference... so i need something which will sum from the number in the cell to the left of the formula to the previous bold number in that column.


OR


b) have a formula which can refer in part to hidden cells & in part not. hence in the data above, if rows 2 & 3 are hidden, i can put in B4 =SUM(OFFSET(A1,1,0):OFFSET(A4,-1,0). Then, if all non-bold cells are hidden, I want to copy this formula down and it will always sum between the non-hidden cells... this doesnt seem to work cos there's a different number of hidden cells all the time... is there a way to make it sum between one un-hidden cell and the previous un-hidden cell?


If anyone can help, would be v nice...

Thank you...