IntroductionBased on the principle that this model is easy and user-friendly to apply in practice to forecast the C1 product of MAD Ltd, especially provide information to people who have no skills. on VBA and forecasting knowledge. This model uses a solver, the Holt-Winters forecasting method and VBA to automatically perform a calculation to obtain the forecast result for the next quarter or the entire year. This report will first give guidance on how to use this model and the accuracy of this model. Then illustrate what forecasting system, computer programming, and VBA are and how these theories apply in this model. Finally, indicated the maintenance process of this model and the limitations of this model if the user wants to continue the process. Orientation of this forecasting model In order to obtain the accuracy of the C1 product of the next quarter, the manager must insert the observation data of the current quarter of C1. amount first by clicking at the bottom front of the Excel file. Then it will ask the user to insert the sales amount data of the current quarter. Tap the actual sales number for the current quarter, then Excel will prompt the user to make sure the recorded data is correct. If they are incorrect, the template will automatically exist, the user must press the bottom again to insert the correct data. If the inserted data is correct, Excel will display a result output box which is due to running the Excel solver with minimal forecast error error. Finally, Excel will display a Product C1 message box showing the next quarter's forecast amount and total cost forecast. As data is updated quarterly, updating the current quarter's sales units will improve the accuracy of forecasting the next quarter's sales unit. This model assumes that MAD Ltd will predict the next which...... middle of paper ...... very simplified and automatic. Based on the configuration, it is suitable for MAD Ltd company for long-term operation without complicated input steps and frequent maintenance activities. However, there are still some disadvantages. As this model mainly provides numbers, it is difficult to compare and illustrate errors between actual observation, quarterly forecasts and annual forecasts. Therefore, using a line graph could clearly illustrate the trend and differences between these variables. The user needs to edit the line chart data provided in the Excel file. Based on the situation of product C1 of MAD Ltd company, design this forecasting process to get an optimized result to forecast product C1 facing people from different backgrounds. For future work, this model could also be applied to other products with trend and seasonality, to improve their accuracy and reduce operating costs..