How to split a string by x amount of characters

I have a program where a user enters a list of numbers in the form of a string. This list of numbers is always a multiple of 8.

So the list can contain 8, 16, 32, 40, 48, etc. numbers.

I need to split that string into every 8 characters.

For example, say the user entered "1234123445674567"

How can I split it into a string array where (0) is "12341234" and (1) is "45674567"

Note: The size of the array has to be equal to the length of the string divided by 8.

Like this:

Dim stringArray(txtInput.Text.Length/8) as String

Edit: I know I could do this by making a loop that counts 8 numbers and splits it into an array but that would be lengthy and take a few variables and I know there's a more efficient way to do it. I just don't know the syntax.