Please help urgent - Excel Macro - Code problem

Please please help on this issue..,

Need to create a Dynamic dependent dropdown with unique values

1. In Billing Sheet - Based on Selected Model name, size and color - it should show the available quantity from stock.

Model Name should be as dynamic dropdown box based on selected Model name it should display available size and color. (It should fetch the data from stock)

2. when data is added in Purchase sheet then it should be added automatically in Stock sheet and when data is added in sales sheet then it should be updated automatically in Stock sheet.


Please help me on this, i am struggling in this part for the past 1 Month and i could not proceed further yet.

I have attached the excel sheet maco for your reference.