Bond Yield to Maturity Calculator

I trade fixed-income and I wanted to have a better feeling of the potential return of an instrument given my set of circumstances. 

With this little tool, you can customise the information to get your Yield To Maturity. 

To do so, you can enter the maturity date, the price, some of the costs such as broker fees and stamp duties. 
I added a personalised tax rate on coupon which depends on countries and personal circumstances. 

The calculation contains two approximations: 

I have not factored in the reinvestment of coupons with the same instrument. I find it not applicable to my real life. 

I supposed the instrument be held to maturity and no further brokerage costs be born at maturity. 

Link to download the spreadsheet.