How can I “ReDim Preserve” a 2D Array in Excel 2007 VBA so that I can add rows, not columns, to the array?

Question

I\'m working with a dynamic array in Excel VBA. The number of columns (m) is fixed, however, I do not know how many rows (n) will be required.

The help documents st

Answer 1

One way to do what you want is to use a 1-D array that contains 1-D arrays instead of a 2-D array. Then you can ReDim Preserve the outer array all you want. If you're returning the outer array from a function, Excel will do the right thing and coerce it to a 2-D array.

For example, the function below will return a 3x2 array to the cells it's called from:

Public Function nested()
    Dim outer
    outer = Array(Array(1, 2), Array(3, 4))

    ReDim Preserve outer(1 To 3)

    outer(3) = Array(5, 6)

    nested = outer
End Function

My answer to these questions might also be useful to you: Pass multidimensional array into Excel UDF in VBA and VBA pasting 3 dimensional array into sheet

Of course, if you're not returning this from a UDF, you'll have to coerce it yourself. An easy way to do that without writing looping code is to do this:

Dim coerced
coerced = Application.Index(outer, 0, 0)

This is just calling Excel's built-in INDEX function, and the zeros mean that you want back all of your rows and all of your columns. Excel will coerce your 1-D array of 1-D arrays to a 2-D array automatically. (Caveat: there are some size limitations, but they are much bigger than 10x20.)