Tracking Flexi Time in Excel

I'm trying to create a sheet which will automatically calculate both the time worked and any flexi time earned.  If my working day is 7 hours and 24 minutes, see example below.

The formula in the Total column is simply D-C-B but after some issues with this field not calculating correctly, I'm using =MAX(D-C-B,0) instead.

The formula in the flexi column is the Total column minus another cell which contains 7:24 (daily hours). 

Where the result is a positive figure, there is no problem and the formula works correctly.  Where the result is a negative, I get ########, instead of -0.24.

I've been able to resolve this by using  -  =IF(E14-$K$2>0, E14-$K$2, TEXT(ABS(E14-$K$2),"-h:mm"))

Where column E is the Total column and K2 is the column which contains the 7:24 figure.  Cells are formatted as [h]:mm;@

However, what I then want to do is sum the figures to give an overall total of the flexi time adding positives but subtracting negatives e.g. 0.26+0.26+1.06-0.24  but all I get is #VALUE! error

Can anyone help with a formula which will allow positive values to be added and negative values to be subtracted?

Thanks in advance

Lori