One Patient = lots of operations, admissions

Hi

Hoping this is a simple one

 using a detailview form and a gridview

patients detail are shown in the details view and a list of all the operations(gridview) this patient has had, got a hyperlinkfield which go to another page displaying info on that operation

If I click on the hyperlink it will only show me one record regardless which record i select (Follow me so far) how do I get it to go to the correct selected record

DataNavigateURLField = Hospitalno,OPGUID (OPGUID as thats the only unique item on that record)

DataNavigateURLFormatstring = operation_letters.aspx?HospitalNo={0}

have tried DataNavigateURLFormatstring = operation_letters.aspx?HospitalNo={0}&OPGUID={1}

 

but no joy :-(

 

Regards
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