> For the complete documentation index, see [llms.txt](https://docs.uibakery.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.uibakery.io/how-tos/custom-code/custom-validation.md).
# Implement custom validation
It might happen that you need to implement the advanced validation of the table or form fields based on a certain condition or data source request while editing or creating new records.
In the use case, we will set up validation of a date\&time field while editing a table record. If the validation fails, the edit action will not be executed and a user will see an error.
1. Create a multi-step action. Add a **Condition** action as a first step. Specify the validation code, e.g.: `return new Date({{ui.table.editedRow.data.end_date}}) >= new Date({{ui.table.editedRow.data.start_date}});`
2\. For the **True** condition, add the edit action. For the **False** condition, add a **Code** action and specify the code with your custom error message, e.g.: `throw new Error("Start date can't be greater than end date.");`
3\. Next, proceed to the **Config** section of the action - **Toasts**. Tick the error message and refer to the action as `{{actions.yourAction.error.message}}`
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