Textbox Validation Check When Save Or Update Button Click

I use VB 2008. I want to check that text boxes have correct data but not at key pressed key down event. I want to check when user fill the form if all have correct data then insert into database otherwise get focus of specifiq textbox which have wrong data. I see many examples but all is applied on keydown keypress etc events. I just need a class i send Textbox as object in that which return true or false. I need one method in that class which check only numbers with decimal point and limit decimal places to 4 digit.e.g 12345.9876 and other method check A to Z and a to z with some special charecters like @ # $ % & ! ;