Option Explicit
'====================================================================================================
Sub t()
Dim rng As Range

Set rng = Selection
If Not GetFullCells(rng, True, True) Then Exit Sub
MsgBox rng.Address(False, False, xlA1, True)
End Sub
'====================================================================================================
Function GetFullCells(rng As Range, Optional MsgTrue As Boolean, Optional MsgFalse As Boolean) As Boolean
Dim rngUR As Range, rngV As Range, rngF As Range

Set rngUR = Intersect(rng, rng.Worksheet.UsedRange)
If rngUR Is Nothing Then GoTo no

    If rngUR.Count = 1 Then
        If Len(rngUR.Value) Then Set rng = rngUR: GoTo yes
    Else
        On Error Resume Next
        Set rngV = rngUR.SpecialCells(xlCellTypeConstants, 23)
        Set rngF = rngUR.SpecialCells(xlCellTypeFormulas, 23)
        On Error GoTo 0

        If rngV Is Nothing Then
            If Not rngF Is Nothing Then Set rng = rngF: GoTo yes
        Else
            If rngF Is Nothing Then Set rng = rngV: GoTo yes
            Set rng = Union(rngV, rngF): GoTo yes
        End If
    End If

no: If MsgFalse Then MsgBox "Range" & vbLf & rng.Address(0, 0, xlA1, True) & vbLf & "DOES NOT CONTAIN FULL cells!", vbInformation, "GetFullCells"
Exit Function

yes: GetFullCells = True
If MsgTrue Then MsgBox "Range with ONLY FULL cells" & vbLf & rng.Address(0, 0, xlA1, True) & vbLf & "was CREATED!", vbInformation, "GetFullCells"
End Function
'====================================================================================================