Forms :: Tax Calculation Cannot Be Inserted In Database

I have created a From with some Fields: Name, Surname, Netto Price, Tax (%) and Gross Price..... to make a invoice.

The Problem is that i cant insert the data from: Tax and Gross Price in to the DB.I have tried this:

select Tax Field--> Property Sheet -> Control Source: =[Price]*0,19

example:
Netto Price: 100
Tax 19%-- =[Price]*0,19 = 19

Now I get the correct values ​​displayed in Field Taxes.But this this sum cant not insert in to the Database.I use MS Office 2013.