Advance Excel Help

Hi All,
I have 2 sheets in a workbook. One is a Covering Letter and the other is a Quotation. The quotation has lot's of options and is very complex. One of the option is Branch (Since we have different branch offices) and a drop down list is available to select the appropriate branch. Each branch has it's own letter head.
What I want Excel to do is when a branch office is selected, the letter head for the entire workbook should change to that of that branch. I have all the letter heads as images in a separate folder on desktop. At the moment the letter head logo is pasted in Header section of the workbook. If a particular branch is selected from the drop down list, can Excel change the letter head in the Header section to that of the selected branch ?
Is it possible or I am asking for something weird and impossible ?
Come on guys need your help.
Thanks Alot

Dear Ms. Huda
Since you had specifically sought help from GUYS, i wish to look into your requirement. Kindly do submit your EXCEL SHEETS for reference, which are missing. Do mark a copy to my email id as well. If i can't do then, i will get it done from my colleague
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Looking forward to hear from you at the earliest.
With profound regards

Dear Mak,
here you may use mail merge option. Type the letter head in word and clik on mail merge and pull the data from excel sheet.
Try youverself you will learn it very easily.