Filter Combo box items based on another multiselect Combobox

Team,

We have some challenges in powerapps form to filter the items based on the selection we make in combobox.

To elaborate,

We have Main List(A) and child List (B).

1) In child list(B) we have 3 Fields like Products, Productgroup and ID field.

2) In Main List(A). We have 3 fields like SelectedProduct and Selected ProductGroup.

Now, we have designed powerapps form in Main list(A). So in Main List(A)- we have created two comboboxes(combobox1 & combobox2) to pull the values from child list(B).

combobox1 will pull the values from child list(B) Products field.

combobox2 will pull the vlaues from child list(B) Productgroup field.

The challenge here is when we select multiple items in combobox1 the combobox2 will filter the last selection made in combobox1. It is not getting appended with existing values.

Can you please help us on this.

Thanks,

Dhana