I have a routine that calculates an assigned number based on the date that is
entered. I have recently changed the code so that it now calculates the
number without me having to give a starting number for each year. This means
that the code loops starting from 2007 to calculate the beginning number for
each year after. I created an array to store as many years after 2007 as the
years increase. It is a one dimensional array.
My question: Is there a simple way to tell whether the array has been filled
or if it is empty on the first time through the routine without getting an
error?

Y would be the year of the date needed. I did not include all of the code.
I created the Iserror routine to try to determine this but I think there must
be a better way.
Once the array has been filled and the program running it will save a lot of
time not to have to recalculate each year again.

Function WDXFind(Y)
YY = 2007 ' starting year
WDX = 1 ' 1/8/2007 starting point for calculating assigned number
for 2007
N = 1 <- dimension
i = 0 <- index

WDXTF = False
On Error Resume Next
If IsError(UBound(WDXHold)) Then
WDXTF = True
End If

If WDXTF Or UBound(WDXHold) < Y - YY Then <- The resume Next lets the
program continue on the first run through. The UBound(WDXHold) gives
"Superscript of Range" error message.

Do Until YY = Y
..
..
ReDim Preserve WDXHold(N)
WDXHold(i) = WDX
N = N + 1 <- dimension starting at 1
i = i + 1 <- index starting at 0
YY = YY + 1 <- increases the year to calculate next
Loop
WDXFind = WDX
Else
WDXFind = WDXHold(Y - 2008)

End If
End Function