Update Field on Other app ?

Update Field on Other app ?

Hi,

I have 2 apps one is QAQI App and other is Sales App in QAQI app i have form which is EMS form in that i have field Account which is lookup from Account form which is from sales app i want when in ems form i select account field and if any value added in Call dispatcher name field then it should update in Account form field call dispatcher name  which is on other app in sales app .

Let me know any function ,script.

Thanks