Need to amke over the sheet change for two placeses for every colum every record ...

[Neonlinks]

Hi, everyone,
Hope to fund an easy way to make the change to the sheet:

I need to change the calculation with one extra value (From one cell) for every column (24) for every record (30).

I am using Excel 2007.

Example:
Change from: F18*0.50
Change to: (F18+ F19)*0.50

Record holds: F28 to F45 with 24 (F, G , H, I, J, ... to Z, AA, AB) Rows.

The Record is a 18X24 in size and is 30 Records for the sheet.
Each Record have two places need to change, F39 & F40 and extend from F to AB.

Any help would be very much appreciated.

[stnkynts]

Is it possible to upload a copy of your workbook?

[Neonlinks]

Thank you for reply and asking.
I prefer not to upload the sheet it is a lot more info contained.
If I have to make change it will take me hours to do about 30 sheets.
Just asking if there is a easier way even just change one row (24 cells) at a time will save me a lot of time.
Any suggestion would be very much appreciated.