How do I Merge two Arrays in VBA?

Try this:

arr3 = Split(Join(arr1, ",") & "," & Join(arr2, ","), ",") 

Unfortunately, the Array type in VB6 didn't have all that many razzmatazz features. You are pretty much going to have to just iterate through the arrays and insert them manually into the third

Assuming both arrays are of the same length

Dim arr1() As Variant
Dim arr2() As Variant
Dim arr3() As Variant

arr1() = Array("A", 1, "B", 2)
arr2() = Array("C", 3, "D", 4)

ReDim arr3(UBound(arr1) + UBound(arr2) + 1)

Dim i As Integer
For i = 0 To UBound(arr1)
    arr3(i * 2) = arr1(i)
    arr3(i * 2 + 1) = arr2(i)
Next i

Updated: Fixed the code. Sorry about the previous buggy version. Took me a few minutes to get access to a VB6 compiler to check it.