Notes

function LTA (x as integer) as double
RowVal = 1

you call the LTA or the STA based on what windowSize you give the sub
the windowSize is one of the parameters of the sub
ComputeLSTermAverage(windowSize, dataLength, ....) ToCol
so when you're actually using the sub
that's when you input it
you say
Call ComputeLSTermAverage(LTAsize, ..., ...)
datalength will still be the same - it's just the output from the FindNumberOfDataPoints function
and the writeToCol is which column you need the output
which is column 2 for LTA and column 3 for STA
on the side of the data, it tells you the LTA size and STA size

you just need to put that in as the first parameter you need
you do 2 calls of the sub
Call ComputeLSTermAverage(LTAsize, ..., ...)
Call ComputeLSTermAverage(STAsize, ..., ...)

Function ComputeAverage
1 - FindNumberOfDataPoints function
2 - first and last line
and 3 - a total
average is obviously just the numbers added up divided by how many numbers there are
so you use a while loop, that adds each number to a variable
so it'll look like
total = total + ActiveSheet.Cells(row, col)
and then row = row + 1
and after the while loop is complete, you do average = total / number of data points

In the computeaverage function How do you pick where your data starts and ends
that depends on what parameters you give for firstRow and lastRow
Use the constants at the start of the program
and a loop function
you just use the variables firstRow and lastRow

variable = ComputeAverage(value, value)
I defined a value called I and just said for i = firstrow to lastrow

Row = data_row_start
If ActiveSheet.Cells(row, LTA_COL) <>"" then
ActiveSheet(row, RATIO_COL) = ActiveSheet.Cells(row, STA_COL) / ActiveSheet.Cells(row, LTA_COL)
Row = row + 1
EndIf
while loop
Try a for loop from data row start to whatever ur variable for amount of data points is
With the if statement u have within it
That worked on mine
Stop Sub : Exit Sub