MSGBOX only if valid time is entered in a cell

Hi ALL,

I have a worksheet where I have to work with different time calculations.

The last part where I am struck is : I require a MSGBOX only if the cell has a valid time value ( including the time ). The text box should NOT appear on negative time values or at text / numeric or blank value.

I am also encloding the sample file to play around with.

Any suggestion would be of great help to me.

Thanks

SAHDEV