@mywolfe02 gives a static range code so his inRange works fine but if you want to add dynamic range then use this one with inRange function of him.this works better with when you want to populate data to fix starting cell and last column is also fixed.
Sub DynamicRange()
Dim sht As Worksheet
Dim LastRow As Long
Dim StartCell As Range
Dim rng As Range
Set sht = Worksheets("xyz")
LastRow = sht.Cells.Find("*", SearchOrder:=xlByRows, SearchDirection:=xlPrevious).row
Set rng = Workbooks("Record.xlsm").Worksheets("xyz").Range(Cells(12, 2), Cells(LastRow, 12))
Debug.Print LastRow
If InRange(ActiveCell, rng) Then
' MsgBox "Active Cell In Range!"
Else
MsgBox "Please select the cell within the range!"
End If
End Sub