primo basically nailed the stringBuilder usage, here a little example:
Uses "console", "stringBuilder"
' this will store the numbers:
Dim builder as new StringBuilder()
' access the numbers virtually:
Dim myNumber() as Number At 0
Dim i As Long ' just to list our arrays elements
' add a few elements, type Ext equals Number, that's why MKE$:
builder.Add(MKE$(0.12345)) ' the first element be 0.12345
' just append a bunch of new elements:
' and some more
builder.Add(MKE$(6.666, 7.777))
' now let's read what we have:
' put the virtual array onto the string:
string builderData = builder.ToString() 
Redim myNumber(Strptrlen(Strptr(builderData))/SizeOf(Number)) At Strptr(builderData)
' list what we have
For i = 1 to UBound(myNumber)
  PrintL i, myNumber(i)
I may add direct pointer to string in stringBuilder as functionality, if there is interest. That would skip the step with assignment to temporary string variable, making it even faster