Making Access database Form more dynamic to Data Input

Question

I'm a beginner at MS Access. and I have created a local database to work on; what I want to do is the following:

1. If the textBox named "Number" starts with specific digits, the ComboBox value to be automatically determined to x value. if we can replace the Combobox with just a label that automatically updates the value based on number textbox, It'd be better, aesthetically.

2. I want this field to be automatically counted from another list that is being input by the user himself. Instead of individually counting each approved case, it'll pull off the approved cases BASED on a specific response code "0". I tried this solution and it just does NOT work.

   =DCount("[Response code]","Information Subform","[Response code] = '0'")

So for example, if the user inputs data as the following, this field should return with "2" automatically instead of the user counting them manually based on Response Code = 0

3. I want to my list to perform the following function: if selected a specific value, change the context of a textbox. It should act as a timesaver to write a specific dialog or script for the user.