=1-2+2-4+4-10+10-15

=ABS(1-2)+ABS(2-4)+ABS(4-10)+ABS(10-15)

=1+СУММ((2-2);(4-4);(10-10))-15

Option Explicit
'v2
Private Sub CommandButton1_Click()
    ActiveCell.Formula = ConnectText
End Sub

Private Function ConnectText() As String
    Dim cb As Object, ss As String, iCount As Long
    ss = "="
    For Each cb In GetControlColection("TextBox")
        iCount = iCount + 1
        If IsNumeric(cb.Value) Then
            If iCount Mod 2 = 1 Then
                ss = ss & "+ABS("
            End If
            If cb.Value >= 0 Then
                ss = ss & "+" & cb.Value
            Else
                ss = ss & cb.Value
            End If
            If iCount Mod 2 <> 1 Then
                ss = ss & ")"
            End If
        End If
    Next
    ConnectText = ss
End Function

Private Function GetControlColection(sTypeName As String) As Collection
    Dim col As New Collection
    Dim cb As Control
    For Each cb In Me.Controls
        If TypeName(cb) = sTypeName Then
            col.Add cb
        End If
    Next
    Set GetControlColection = col
End Function