Circular reference mistake

[toddbob]

I have a data on worksheet 1 column A = month column D = Salesman column E = Branch. I am also using validation for a drop down list in column E.
On worksheet 2 column A = branch name column B = number of times in a given month a branch name appears on worksheet 1 column E using following formula: =SUMPRODUCT(((Sheet1!$E$2:$E$800)="Atlantic")*1,(--(MONTH(Sheet1!A2:A800)=1)))
On worksheet 4 I have column A = salesman column B = branch for Vlookup reference array.
Now my problem on worksheet 1 I decide to use a Vlookup function so everytime I enter salesman (column D) the branch (column E) automatically fills in formula follows:
=VLOOKUP(D:D,Sheet4!A1:B30,2,FALSE)
For some reason this creates a circular reference on worksheet 2 in my B column. Why? I can get along with my work without Vlookup but it makes data entry less time consuming.

thank you
Todd

[Mandy11]

Send me an example of the spreadsheet.