hello every body

my problem relate from combo box.
for example iam using three links in my home page
(1) contact us
(2) technical support
(3) sales

the fourth will be contact form .

when i click on contact us link the page jump on contact form

similarly when i click on technical support link , the page jump on contact form

similarly when i click on sales link , the page jump on contact form.

mean all three pages link from contact form page.

now contact form consist of a combo box following r the values included in combo box.

(1) choose (which will be by default value)
(2)technical support
(3) sales

now i want that when i click on contact link from my home page the page jump on contact form , in contact form the combo box value will be by default (which show choose)so that we can choose any value.

now my main problem is that (how its possible that, click on technical support link from my home page the page jump on contact form , in contact form the combo box value will be "technical support") now we dont need to choose value.

similarly (how its possible that, click on sales link from my home page the page jump on contact form , in contact form the combo box value will be "sales") now we dont need to choose value.