Pres Alt+F11 to open the VBA editor. Right-click where it says VBAProject([name of your file]), Insert, Module. Then paste this code in there:
Total = 0
For Each c In Range("B1:E10").Cells
If c = "Cost" Then
Total = Total + c.Offset(0, 1).Value
Range("A1").Value = Total
Just replace the the 2 instances of "Range" with the appropriate values for your file. The first should be the range you want to search and the second is where you want excel to paste the sum.
You can set this macro to a hotkey so that you can just click it once on each sheet easily. Back in Excel, click View, Macros, View Macros, select the macro you just created (SumCost), click options, and add a letter in the box after "Ctrl+".
Remember that as written the macro performs the code on the active sheet.