Reverse Lookup 2D array in VBA to get Column name from list of data

Question

Hi I need help using Excel VBA for large volume 2D matrix data, how to get the Column name from the data table based on a specific set of lookup values from another sheet, a reverse lookup using VBA code?

The look up value can be duplicated but we want to capture its column name where it occurs first, see below example.

any ideas how?

Lookup Value	Col Name
A101	L2
A102	L3
A201	L2
A304	L5

2D Table

ref	L1	L2	L3	L4	L5
Cx1	A100	A101	A102	A102	A102
Cx2	A100	A101	A102	A103	A104
Cx3	A111	A111	A113	A114	A114
Cx4	A200	A201	A201	A201	A201
Cx5	A300	A301	A302	A303	A304

Answer 1

There's no need for VBA. If you are looking for the first column in which Lookup Value appears, you can use:

=INDEX(Table1[#Headers],AGGREGATE(15,6,1/(J2=Table1)*COLUMN(Table1)-INDEX(COLUMN(Table1)-1,1),1))

Note that I used a Table , but you can use regular addressing if you prefer.

Algorithm

• create a 2D array of {TRUE,FALSE} based on the equality
• 1/theArray => array of {1,#DIV/0!}
• Multiply by the column number; then subtract the first column of the Table (minus 1) to create a number suitable for indexing into the Table
• Use the AGGREGATE function with the SMALL argument, and the option to ignore errors, to return the smallest index column argument for the lookup value
• Use INDEX to return the appropriate value from the #Headers array

If you must use VBA, you can create a User Defined Function:

Option Explicit
Function Header(lookup_value, table As Range) As String
    Dim c As Range
    Set c = table.Find(what:=lookup_value, LookIn:=xlFormulas, lookat:=xlWhole, searchorder:=xlByColumns, searchdirection:=xlNext)
    If Not c Is Nothing Then Header = table(1, c.Column - table.Column + 1)
End Function