To clarify - you are concerned that taking the omega 3 fish oil capsules and your multivitamin tablets in combination may inadvertently cause you to take a potentially dangerous daily intake of Vitamin A. Is this assumption correct?
Proceeding on the basis that it is, a couple of points / comments.
1. Cod Liver Oil ( and I am also making the assumption that this is what you mean when you talk about cod oil tablets) is a supplement containing high levels of Vitamin A, D and the essential fatty acids EPA and DHA. Used in adults principally for its seeming benefits in rheumatoid arthritis etc, and in kids usually as a convenient source of vitamin D to prevent rickets.
2. Centrum Multivitamin tablets - contain approximately 70% the RDA of Vitamin A, although a significant proportion of that is as beta carotene , a precursor to vitamin A ,which the body then converts - so its essentially harmless.
3. Omega 3 fish oils contain no vitamins, just EPA and DHA. Their principal health claim and the best evidence available for any sort of clinical effect is for cardiovascular health. They are also claimed to be beneficial in reducing pain in rheumatoid arthritis, although there is less direct evidence for this. More recently, there have been some claims regarding attention defecit disorder in kids, but the evidence to date is poor.
So , if you were taking centrum supplement pills and cod liver oil - then there is a chance that you were close to or even exceeding your suggested maximum recommended daily allowance.
Now however, taking centrum multivitamin tablets and omega 3 efa fish oil capsules ( which contain no vitamin A) you are well within the maximum suggested daily limit.
RDAs are theoretical, and the suggested maximums are also theoretical. It is not an exact or even particularly exact science, and is extremely dependent on the status of he individual with regard to their general health, nutrition, weight,