Excel VBA: delete values on multiple columns

Hello experts,
I have the following procedure:

Sub Add_Values_Multiple_Columns()
    Dim wsActive    As Worksheet
    Dim wsOutput    As Worksheet
    Dim strCol      As Variant
    Dim strColList  As String
    Dim lngLastRow  As Long
    Dim lngLastCol  As Long
    Dim shName      As String
    
    Application.ScreenUpdating = False
    
    Set wsActive = ActiveSheet
    
    strColList = InputBox("Please report column letter(s) following by ; in which you want to apply procedure," _
                          & ": A for single column A;C;D for multiple columns", "Choose Column Letter(s)")
    If strColList = vbNullString Then
        MsgBox ("No input!")
        Exit Sub
    End If
    
    For Each strCol In Split(strColList, ";")
        If Not ValidCellReference(strCol) Then
            MsgBox strCol & " is not a valid column letter.", vbExclamation
            Exit Sub
        End If
    Next strCol
    
    Set wsOutput = Worksheets.Add(after:=Worksheets(Worksheets.Count))
        
    For Each strCol In Split(strColList, ";")
        lngLastRow = Range(strCol & Rows.Count).End(xlUp).Row
        If wsOutput.Range("A1") = "" Then
            lngLastCol = 1
        Else
            lngLastCol = wsOutput.Cells(1, Columns.Count).End(xlToLeft).Column + 1
        End If
        lngLastRow = wsActive.Range(strCol & Rows.Count).End(xlUp).Row
        wsActive.Range(strCol & "1:" & strCol & lngLastRow).Copy wsOutput.Cells(1, lngLastCol)
    Next
    
    shName = "Output_" & Format(Now, "yyyymmddmmss")
    wsOutput.Name = shName
    Application.ScreenUpdating = True
    Exit Sub

Error_Routine:
    MsgBox Err.Description, vbExclamation, "Something went wrong!"
    
End Sub


Function ValidCellReference(ByVal str As String) As Boolean
Dim rng As Range
On Error Resume Next
Set rng = Cells(1, str)
On Error GoTo 0
If Not rng Is Nothing Then ValidCellReference = True
End Function

Select allOpen in new window

Which allows me to add values on multiple columns.
I would like to take it as a reference to cover the following need:
1-Inputbox report the columns in which you want to delete values.
2-Delete values (Value="") on columns reported as of row 2.
I attached dummy file with input and expected result in output sheet when I report column C and E on Inputbox.
If you have questions, please contact me.
Dummy-file-delete-values.xlsx