Try to use :

LOCATE FOR upper(alltrim(mac1))=upper(alltrim(thisform.grid1.column1.text1.value)) AND upper(alltrim(typ))=upper(ALLTRIM(thisform.grid1.column2.text1.Value)) AND upper(alltrim(peri))=upper(alltrim(thisform.combo1.displayvalue))

If this won't work, please provide me the value of all the text boxes and fields.

thanks.