excel – Reveal Column by clicking on the Cell in it

The problem is I can’t back original size of the column when I leaving it.

Is this what you are trying?. This stores the previous width and column number in a variable.

Dim prevWidth As Long
Dim prevCol As Long

Private Sub Worksheet_SelectionChange(ByVal Target As Range)
    If prevWidth <> 0 And prevCol <> 0 Then
        Columns(prevCol).ColumnWidth = prevWidth
    End If

    On Error Resume Next
    prevWidth = Target.ColumnWidth
    prevCol = Target.Column
    Columns(prevCol).EntireColumn.AutoFit
    On Error GoTo 0
End Sub

Here is a simple example where I sacrifice the TOP two rows that holds width for active and inactive columns:

You can obviously pick any row, maybe even use a named range in case you add/delete rows. But this is the code I used:

Private Sub Worksheet_SelectionChange(ByVal Target As Range)

Dim rng As Range
For Each cl In Range("A1:E1")
    Set rng = Intersect(cl.EntireColumn, Target.Columns)
    If Not rng Is Nothing Then
        cl.ColumnWidth = cl(1)
    Else
        cl.ColumnWidth = cl(2)
    End If
Next cl

End Sub

EDIT

Another interesting thing to do is to create a Dictionary upon activating the specific sheet. Fill that dictionary with the columnwidth of each column in the specified range. The rest is a small adaptation of the code I showed above.

Public dict As New Scripting.Dictionary
Dim rng As Range, cl As Range

Option Explicit

Private Sub Worksheet_Activate()

For Each cl In Range("A1:E1")
    dict.Add cl.Column, cl.ColumnWidth
Next cl

End Sub

Private Sub Worksheet_SelectionChange(ByVal Target As Range)

For Each cl In Range("A1:E1")
    Set rng = Intersect(cl.EntireColumn, Target.Columns)
    If Not rng Is Nothing Then
        cl.EntireColumn.AutoFit
    Else
        cl.ColumnWidth = dict(cl.Column)
    End If
Next cl

End Sub