Insert commas to textbox

Question

Hi all,
I want Vb.net code to insert commas between numbers in Indian format , i.e. 12345678 should be taken as 1,23,45,678. And this value will be taken for other textbox for further calculation. Like txtSTP.text=(1,23,45,678) * 0.12
Thanking you in advance
Veeraraghavan