[[enecumene]]

A ver, intenta lo siguiente:

Código Delphi [-]
Var
Suma: Double;
Campo:  TField; 
Begin
     Suma:=0;
     Try
        With query1 Do Begin
             DisableControls;
             ElCampo := fieldbyname('Field');
             First;
             While Not EoF Do Begin
                   Suma := Suma + Campo.AsFloat;
                   Next;
             End;
        End;
     Finally
        query1.EnableControls;
     End;
     Edit1.Text := Floattostr(Suma);
End;

Saludos.