Excel Compare 2 columns in 2 different sheets

Hello,

I'm having some trouble trying to figure something out.

I have an Excell workbook with 2 worksheets.
Each worksheet contains 2 columns of data.

1st column (in both worksheets) is a column with usernames
2nd column (in both worksheets) contains different numbers

The 1st column in the 2nd worksheets contains more usernames than the
1st column in the 1st worksheet.

What I need to do:
I need to transfer the values of the 2nd column of the second worksheet to a
new column in the 1st worksheet.

Sounds easy but:
I need to compare the usernames of the 1st column in the 2nd worksheet to the
usernames in the 1st column of the 1st worksheet. If there are usernames in the 1st
column of the 1st worksheet that don't appear in the usernameslist of the 2nd worksheet
the 2nd column of the 2nd worksheet needs to skip that username.

Example:

(1st worksheet)
Column 1: Column2:
USER1 1123
USER2 1128
USER3 1129

(2nd worksheet)
Column 1: Column2:
USER1 999888
USER7
USER3 999889


USER7 doesn't exist in the 1st worksheet so I need to skip that user when I copy the
2nd column of the 2nd worksheet.

The result I'm looking for is a way to get this result:
(1st worksheet)
Column 1: Column2: Column3:
USER1 1123 999888
USER2 1128
USER3 1129 999889

So if USER1 (1st worksheet) equals USER1 (2nd worksheet) , copy 999888
to the 1st worksheet in a new cell.

I hope somebody knows what I'm trying to say :-) Sorry for my extremely long question :-)

THANKS !!!!!!!!!