Sweat Equity Clause For Senior Employee In A Startup

Hello,
We are planning to hire a senior resource for our startup offering him some sweat equity as part compensation (e.g. 500 shares, 250 shares vesting at end of one year and remaining at end of second year. Please help me with the clause we need to add in the offer letter regarding this.
Thanks in advance!

Dear RKAY,
I suggest you include a clause stating--'On completion of one year working and subject to satisfactory performance,-------number of shares will be transferred in your name and on completion of two years of working/service in the organisation and satisfactory performance, ------number of shares of----- will be transferred in your name.It be noted that share price is subject to change and no commitment what so ever is being made with regards to market value of the shares.'
Hope this meets your requirement.
Col.Rathi