interactive inventory management

When a specific customer orders for a product, if the customer's stock of that product is insufficient, the order must be met from the dummy stock of that product. I also share a picture of how the table should be based on a single product. but i have much more product types.i am also sharing the sample output table for one product. in addition, i also add the measure that i wrote it but it does not work properly. i am glad that if you will help me:)

sample output:

measure:

measure=

var product=SELECTEDVALUE(table1 [productid])

var dummy=SELECTEDVALUE('dummytable'[productid])

var customer=SELECTEDVALUE(table1[customer])

return

 IF(urun= dummy && [ending]<0 && customer <> dummy ,[dummy stok],[ending])