In reports functions can be used on the control members contained in the report. Fig. 15 you can see the attitudes for the computation of the turnover difference of the transactions. The indication area diff_Auszahlng_Einzahlung maintains as ControllSource the function
=[txt_Auszahlung]-[txt_Einzahlung]
on the fields txt_Auszahlung and txt_Einzahlung. With a control
member, which indicates a function,
the propertie TableSource is not set.