Need help.

I have three columns of data:

Column A = Employee ID's
Column C = Employee ID's
Column D = System Name

Column C contains all company Employee ID's and Column D contains the
associated system name.

I am taking certain sets of Employee ID's and putting them in Column A. I
would like to compare each ID to the range of ID's in Column B and return the
assigned system name from column D into Column B.

Emp ID(1) Matched System Name Emp ID(2) System Name
5 Sys00005 1
Sys00001
6 Sys00006 2
Sys00002
7 Sys00007 3
Sys00003
4
Sys00004
5
Sys00005
6
Sys00006
7
Sys00007

I hope this outlines what I am looking for. The data put into column A can
vary in array length but will never be larger than the data array in column
C/D. I am sure this is easy for the experts but I have been cruising the
discussion boards and can not find a prior discussed solution.

The purpose for this is I need to search smaller sets of ID's across
thousands of company ID's to get system names which I can copy pasted into
another worksheet.

Thanks!

TKD