How to set a depreciation fixed amount for an asset

Hello,

We are using a "Flat" Method type with "NBV" as Calculation Basis with a ratio acordind to the remainig useful life of the asset, but the customer needs to change the depreciation method to set a constant depreciation amount for the remaining useful life. Is is possible to do this? This is not possible to do with STL method because I need the asset to keep depreciating with the same amount as the last year. I will attach supporting documentation to question.

I await your comments,

Thanks!

Gabriel