I am trying to execute a code at a specific time using "timer" function from vb.net and combobox to select hours and minutes

i am trying to create an application that has 2 comboboxes , or text , or anny kind of time pick-ing interface, select the FROM: time to TO: time and the timer to start , and when the difference between the hours is elapsed the timer stops! can u please help me ?

Basicly i am selecting from :hour(min:sec) , to: hour (min:sec) and then set the timer interval = to the deference from hour in combo box 1 and hour from the combo box , text , etc 2 ! thank you i am using visual studio .vb.net