I have two sheets. One is where I want the data to be, while the other is my
key.

On my "key" sheet, I have four columns of data as such: dept, dept name,
activity, activity name. But for each department, there could be 2-6
different activities for each one. I have it set up like the following:
a b c d
100 admin 100 general
100 admin 101 HR
100 admin 102 IT

On my data sheet, I have a number of columns but am trying to bring back the
activity name to the data sheet set up like so(dept, dept name, activity,
activity name). The dept # and activity #'s are the data sheet. I have no
trouble with the dept name since I used a vlookup formula. My trouble comes
to the activity name. I tried to use
=IF(ISNUMBER(MATCH(C3,'Act Chart'!A:B,0)),VLOOKUP(C3,'Act
Chart'!A:B,1,0),IF(ISNUMBER(MATCH(E3,'Act Chart'!C:D,0)),VLOOKUP(E3,'Act
Chart'!C:D,4,0),""))

I was thinking it would match/lookup the department in column A (from the
Key) and bring back the activity name to my data sheet. It isn't working.