Access VB Code Help

I am fairly good with general code in access. Where my knowledge falls short is anything that has to do with the FOR command and I believe thats where I am at now.

I have a table with 3 columns A, B, C
A is the primary key

I want to populate every record in columns B & C with code when a form control [ControlA] OnChange event fires.

This is where I believe I need the FOR each record command to do this!

Another problem is I need the math to be like the following:
Column B = [ControlA]*Column A
Column C = [ControlA]*[ControlB]*[ControlC]*Column A

I am sure this is some type of update query or similar situation, but figured i would ask which direction to go before I get lost ;)

I am not sure how I add Column A into the equation!

Any help or direction would be greatly appreciated.

Thanks,
Don