Hide/Unhide columns based on whether 'x' appears in that column or not

[BobZZ]

I would like to hide/unhide columns based on whether I put an 'x' in row 1. I presume that I have to determine the last used column and then do a for each along row 1 to evaluate if there is the value 'x' in it. If it does then hide it or unhide it depending on which of the two actions I have chosen. What I need help with is how to reference the column by number so that the for each loop works. With the code below, how can I refer to the "L:L" numerically so that the loop works?
Or, maybe there is a whole better approach than what I am thinking. In any case, any pointers much appreciated.

    Columns("L:L").Select
    Selection.EntireColumn.Hidden = True

[alansidman]

To make this work, need to know the last column containing data. Will that be a constant or will that change? If not a constant, in which row will there always be data to determine the last row.

[BobZZ]

I'm a little confused whether you mean row or column. In any case it is based on a table so row 5 will always have headers and for the most part remains constant. The rows however are dynamic and changes in length with column 4 always being populated because it contains the part number which is the driver of everything else in the sheet.

[alansidman]

This macro will unhide all columns upon execution and then hide only columns having an "x" (lower case) in row 1 of any column.

Option Explicit

Sub HideX()
    Dim lc As Long
    lc = Cells(5, Columns.Count).End(xlToLeft).Column
    Dim i As Long
    Columns.EntireColumn.Hidden = False
    For i = 1 To lc
        If Cells(1, i) = "x" Then
            Cells(1, i).EntireColumn.hiddent = True
        End If
    Next i

End Sub