Variable number of terms in an Excel VBA Formula? - vba

Question

Is it possible to write a formula in VBA for excel such that there are "n" terms in the formula, with the number of terms changing as the value of "n" does?
For instance, say you wanted to code cell a1 such that it was the sum of a2 and a3. Then you wanted b1 to be the sum of b2,b3,b4,b5 and so on such that each column 1 row 1 cell for a range of cells is the sum of "n" cells below it where "n" varies from column to column. Say that all cell addresses you wanted to use are known and stored in an array.
Here is some code to better explain what I'm asking:
For i = 0 to n
Range(arr1(i)).formula = "=" & range(arr2(i)).value & "-(" _
& Range(arrk(i)).value & "+" & Range(arrk+1(i)).value & "+" _
& Range(arrk+2(i)).value & "+" & ... & ")"
Next i
So what I'm looking for is one piece of VBA code that can make a cell formula contain a dynamic number of terms. The code above would make cell a1's value = a-(b+c+d+...) where the number of terms in the bracket is variable, depending on which cell the formula is applied to.
The image here shows an example of what I want to do. I'd like some code which could take "years income" and subtract a variable amount of "expenses" from it, where the number of expenses varies each year (but the number stays fixed for that year). The code needs to use a formula so that the expenses entries can be modified by the user.

Answer 1

Have you tried Array Formula ? :
Array Formula :
An Excel Array Formula performs multiple calculations on one or more sets of values (the 'array arguments') and returns one or more results.
details : http://www.excelfunctions.net/Excel-Array-Formulas.html

Answer 2

Thanks for the suggestions everyone, I found a solution (not a particularly efficient one, but a solution nonetheless) to the conundrum today.
First I created an array which used the "pattern" of the Junk cells to list every cell address which was to be included.
Taking this array, I used a for loop to create a series of temporary arrays with the application.index command. For each temporary array, I used the Join command to turn the list of cells into a single string which I then inputted into a cell formula. Thanks to #thepiyush13 whose array.formula approach inspired this.
Here's some example code to show what I did:
' hypothetical array containing two sets of cells to use
Dim array1(0 To 1, 0 To 1) As Variant
Dim vartemp As Variant
Dim vartemptransposed As Variant
' col 1 will be used to add I10 and I13, col2 I11 and I14
array1(0, 0) = "$I$10"
array1(1, 0) = "$I$13"
array1(0, 1) = "$I$11"
array1(1, 1) = "$I$14"
For i = 1 to 2
'application.index(arr,row#,col#) to create a new array
vartemp = Application.Index(array1, 0, i)
'error if not transposed
vartemptransposed = Application.Transpose(vartemp)
randomstring = Join(vartemptransposed, ",")
totalvalue = 100
'example formula: a1 = totalvalue - sum(I10,I13). a2 = totalvalue - sum(I11,I14)
Cells(1,i).formula = "=" & totalvalue & "-SUM(" & randomstring & ")"
Next i
I needed the code to run this many many times on large lists which are generated dynamically but always hold the same pattern of where the "junk cells" are. Not included in the code, but I also used another array for the cell addresses of where to place the formula.