Sub SetTextboxHeight(frm As Form, ByVal Height As Single)
    Dim ctrl As Control
    
    For Each ctrl In frm.Controls
        If TypeOf ctrl Is TextBox Then
            If ctrl.MultiLine = False Then
                ctrl.Height = Height
            End If
        End If
    Next
End Sub

Private Sub Form_Load()    
    SetTextboxHeight Me, Combo1.Height
End Sub