The ReDim command reallocates the storage space of an array variable.
So for example, if you did the following:
Dim Arr_TestArray(9, 2) as Integer
To create an integer array with 10 x 3 elements, and wanted to resize it to 5 x 5 elements you would do the following:
ReDim Arr_TestArray(4, 4)
You will however lose all the existing data stored in that array unless you use the Preserve command alongside it.
(Note: Arrays have a zero element in .net so by declaring an array length of 4, it will ifnact have 5 elements)