how do I concatenate custom formatted numbers
 

I have three colums I am trying to concatenate they look like this:
A B C
Map Lot Unit
000001 000001 000000

I have had to create a custom format to make all of the zeros show. The
first 2 columns are formatted as 00000# and the last column is formatted as
00000#0.

When I enter the formula in a destination cell (Column D Row 2) I enter the
following formula: =CONCATENATE(A2,B2,C2)

As a result I get only the formula showing in the destination cell if
formatted as "Text", if the cell is formatted "General" I get a total of 110.

I would appreciate any help anyone can give.
Thanks!
Robyn