IF(ISERROR) error excel 2003

excvel 2003
This is a lone workers log he phones in start time & finish time (with random calls during working day)
Getting hash in totals cell (see attached doc) when start time entered in cells D4 F4 H4 J4 L4 N4 P4 totals cell R4 shows ###### ( works ok when finish time entered in cells E4 G4 I4 K4 M4 O4 Q4)tried ( with half hour lunch break Monday Tuesday Thursday Friday)

If possible in place of hash in cell R4when logged in shows 1conditional format cell R4 red, then green when logs out

tried this
IF(ISERROR(D4:F4:H4:J4:L4:N4:P4)),E4-D4+G4-F4+I4-H4+K4-J4+M4-L4+O4-N4+Q4-P4-COUNT($D4:$G4,$J4:$M4)/2*(30/(60*24))

But doing something wrong
Thank you
Ralph