Excel VBA find address and assign to variable then reuse value - vba

Question

I'm trying to find if there's a given title on a cell, pass the address of that cell to a variable and use such location to adjust the size of the column. The reason I'm doing this is because I'm writing several functions which will shift the position of the columns. I'd appreciate it if someone could take a look and tell me what I'm doing wrong.
Option Explicit
Sub adjustColumns()
Dim PONumberCell As String
Dim PONumberAddress As Range
Dim TopLabelinColumn As Range
For Each TopLabelinColumn In Range("A1:Z1").Cells
If TopLabelinColumn Like "PO_NUMBER" Then TopLabelinColumn.Value = "PO"
PONumberCell = TopLabelinColumn.Address
Set PONumberAddress = PONumberCell
PONumberAddress.ColumnWidth = 70
Next TopLabelinColumn
End Sub

Answer 1

edited after OP's further request:
you are confusing a Range object (such as PONumberCell is meant to be) with a String variable one (like PONumberAddress), so
Set PONumberAddress = PONumberCell
doesn't work because you are trying to assign an object variable to a String one
but you can be more effective avoiding the loop and using the Find() method
Option Explicit
Sub adjustColumns()
Dim PONumberAddress As String
Dim PONumberCell As Range
Set PONumberCell = Range("A1:Z1").Find(what:="PO_NUMBER", LookIn:=xlValues, lookat:=xlPart, MatchCase:=False)
If Not PONumberCell Is Nothing Then
With PONumberCell
.value = "PO"
PONumberAddress = .Address
.EntireColumn.ColumnWidth = 70
End With
Else
Set PONumberCell = Range("A1:Z1").Find(what:="PO", LookIn:=xlValues, lookat:=xlWhole, MatchCase:=False) '<--| if it didn't find "PO_NUMBER" then it seaches for a complete match of "PO"
If Not PONumberCell Is Nothing Then PONumberCell.EntireColumn.ColumnWidth = 70
End If
End Sub

Answer 2

Following the comments above, there are a few erros in your code:
Setting the PONumberAddress Range, you need to use the syntax : Set PONumberAddress = Range(PONumberCell) using the address string found in brackets.
To set the column width, use : PONumberAddress.Columns.ColumnWidth = 70.
According to your post, I think you want to do this only for columns where the header text is "PO_NUMBER", therefore you need all the code below inisde your If : If TopLabelinColumn.Value Like "PO_NUMBER" Then.
Code
Option Explicit
Sub adjustColumns()
Dim PONumberCell As String
Dim PONumberAddress As Range
Dim TopLabelinColumn As Range
For Each TopLabelinColumn In Range("A1:Z1").Cells
If TopLabelinColumn.Value Like "PO_NUMBER" Then
TopLabelinColumn.Value = "PO"
PONumberCell = TopLabelinColumn.Address
Set PONumberAddress = Range(PONumberCell)
PONumberAddress.Columns.ColumnWidth = 70
End If
Next TopLabelinColumn
End Sub