Update Values within a addCombo

[KingYapster]

Is there a way to update the values array within a addCombo?

Example:
1.) User first selects a brand from various brands of shoes (Using a combo box)
2.) Then from the selected value of brand, User needs to selects a variant from various variants of shoes (Using a combo box)
3.) Based on the variant and availability, a shoe size combo box is added

So, how can I change the values of variants combo box, based on the selected value of brand?