Inserting text based on another cell of number

Hi what im trying to do is speed up a daily task, each day i get sent an excel sheet and what i have to do is put the initials of the team manager in column B next to each techs id they look after (column G) is there a way of running a macro that would know what initals to insert based on the tech id, so maybe a code that new say ten different number would relate to TH and another 10 numbers would be GS and so on, i attached a copy of the sheet for anyone that could help to look at.

Thank you in advance if there is a way.

You forgot the attachment.

sorry what an idiot now attached

BUMP any ideas anyone