Modules & VBA :: Skipping Controls On Validation Check Before Update

I'm working on a code that checks all blank/null text fields and combo boxes in a form and notifies the user if a field is not filled. The code below works if all fields are required, but I can't use it on forms that have fields that are not really mandatory. I've read somewhere on the net to use tags on the controls i want to skip checking, but that's where i get lost.

Code:
Dim stdResponse As Variant
Dim ctl As Control
' Enumerate Controls collection.
For Each ctl In Me.Controls
' Check to see if control is text box

[Code] .....