Using VBA to set the LinkedCell of an ActiveX Combo Box

Hi all! I'm having some issues with a Combo Box that I cannot for the life of me figure out. I am trying to have a single Combo Box that jumps around to whichever cell the user selects in a specific column on a spreadsheet and to then dynamically change the LinkedCell of the Combo Box to the selected cell. I've gotten everything working except for the LinkedCell part - here's the code I'm currently running with:

PHP Code: 

Private Sub Worksheet_SelectionChange(ByVal Target As Range)
    
    Dim WB_Timesheet As Workbook
    Dim WS_Timesheet As Worksheet
    Dim NumberOfCellsSelected As Integer
    Dim CB As Shape
 
    Set WB_Timesheet = Application.ActiveWorkbook
    Set WS_Timesheet = WB_Timesheet.Sheets("Timesheet")
    Set CB = WS_Timesheet.Shapes("ComboBox_ClientMatter")
    NumberOfCellsSelected = Target.Cells.Count
    
    If NumberOfCellsSelected > 1 Then
        CB.Visible = False
    ElseIf Selection.Count = 1 Then
        If Not Intersect(Target, Range("C6:C10000")) Is Nothing Then
            Dim Position_Left As String
            Dim Position_Top As String
            Dim CB_Height As String
            Dim CB_Width As String

            Position_Left = ActiveCell.Left
            Position_Top = ActiveCell.Top
            CB_Width = ActiveCell.Width + 15
            CB_Height = ActiveCell.Height + 2
                        
            With CB
                .Visible = True
                .Left = Position_Left
                .Top = Position_Top
                .Width = CB_Width
                .Height = CB_Height
                .ControlFormat.LinkedCell = ActiveCell.Address
            End With
        Else
            CB.Visible = False
        End If
    End If
End Sub 


The code keeps bugging out on the line of ".ControlFormat.LinkedCell = ActiveCell.Address". I've tried what feels like a million different formulations of this (including not using the ".ControlFormat" portion, messing around with the stuff after the "=", etc.), but I keep getting the same run-time error '438'. If anyone could help me figure out what I'm doing wrong I would be extremely grateful.

Also, as an aside, if anyone knows how I can use VBA to (i) put the cursor into the Combo Box and (ii) make it to where, upon initially selecting/targeting the Combo Box, it selects all of the text therein (i.e., something akin to pressing "Ctrl+a"), I would also very much appreciate that as well. (This would just be an added bonus and I'm mainly just looking to figure out how to alter the linked cell.)

Originally Posted by Andy Pope

If it's an activex combo box then

                .OLEFormat.Object.LinkedCell = ActiveCell.Address

That did the trick! Thank you so much!!