Splitting Number And Storing It As Individual Digits

I am working on my project for VBA and I need to make a program for Large Factorials sch as 25!, which is too big to fit as a Long-integer. I basically have to find a way around this by storing the numbers as arrays F() and C(). Array F is for the multiplication of each cell of memory, and C is for the carries, which will later be added. I need to separate the hundreds, tens and units of each multiplication.

To Further explain, lets say I have 12!; to find this I would take the previously calculated 11! (by using a loop) and multiply 12 by each memory cell of the array F(). So it's kind of like multiplying by hand, you bring down the units and put the carries on top to be added later. I would store the carries as one or two memory locations over of the current I, or the current loop number. So the units of the mult. would be stored as F(I), the tens would be carried and stored as C(I+1), and the hundreds would also be carried, but this time two cells over, so C(I+2)

The main problem I have is finding the proper code to split the number into units, tens, and hundreds, and then assigning them to their appropriate memory cells within their respective arrays.

Here's what I have so far:

Code:
Dim F(1 To 30), C(1 To 30), N As Integer, Fact As Long, Length As Integer, space As Integer
Sub LargeFactorialCalc()
Open "F:project.txt" For Output As #1

F(1) = 1
N = InputBox("Enter the number you would like to take the factorial of: ")

[Code] .......