vlookup with VBA

here is some code that you might start with. You can't activate an event in Excel on a hover or a double click, but you can capture a selection change. This code opens a reference workbook the first time a specific sheet is actuivated, and then wherever the selection is changed in that sheet, it does the lookup on the reference table and display the message. Note that there are a number of assumptions abou the structure of the reference workbook and the location of the unit numbers.
Put this code in VBA on the sheet object that you want the lookup to apply to. See if it gets close to what you want and we will go from there.

Option Explicit
' Global reference sheet name
Dim ReferenceSheet As Worksheet

' the name of the reference sheet to use
Const ReferenceBookName As String = "Reference.xls"
Dim ReferenceBook As Workbook

' make sure the reference workbook is open
Private Sub Worksheet_Activate()

    ' if the reference book has not yet been opened, then open it and address the reference sheet
    If (ReferenceBook Is Nothing) Then
        On Error Resume Next
        Set ReferenceBook = Workbooks.Open(Filename:=ReferenceBookName, ReadOnly:=True)
        If (Err.Number = 0) Then
            Set ReferenceSheet = ReferenceBook.Worksheets(1) ' assumes the reference sheet is sheet1
        Else ' can't open the reference book
            Set ReferenceSheet = Nothing
        End If
        On Error GoTo 0
    End If
    
    ' reactive this sheet
    Me.Activate

End Sub

' produces a popup message containing data from a table
Private Sub Worksheet_SelectionChange(ByVal Target As Range)

    ' skip this is there is no reference sheet
    If (ReferenceSheet Is Nothing) Then
        Exit Sub
    End If

    ' assumes that the lookup is to occur on values in column A
    ' select only column A and ignore the header row
    If (Target.Column = 1 And Target.Row > 1) Then

        ' lookup the entry in the lookup table which is located in the on the reference sheet
        On Error Resume Next
        Dim theRow As Long
        
        ' assume the reference table is in column A
        theRow = Application.WorksheetFunction.Match(Target.Value, ReferenceSheet.Range("A:A"), 0)
        If (Err.Number = 0) Then
        
            'get the data from the rest of the row
            Dim theType As String
            Dim theYear As String
            Dim theStatus As String
            theType = ReferenceSheet.Cells(theRow, "B").Value
            theYear = ReferenceSheet.Cells(theRow, "C").Value
            theStatus = ReferenceSheet.Cells(theRow, "D").Value
            MsgBox "Unit = " & Target.Value & vbCr & _
                   "Type = " & theType & vbCr & _
                   "Year = " & theYear & vbCr & _
                   "Status = " & theStatus
        End If
        On Error GoTo 0
    End If

End Sub