I have already recieved some help on this one, but now if the user hits the cancel button or enters no value it results in an error/ debug box
I would like it to exit the macro when the cancel button is pressed, and if a value is not entered to display a msgbox telling you that a value was not entered
Can you help me with an if statement or on error line

Here is what I have

Sub standard1(

fconc = InputBox("Enter final conc. (ug/ml or ng/ul)"
fvol = InputBox("Enter final volume (ml)"
sconc = InputBox("Enter conc. of standard (ug/ml or ng/ul)"

MsgBox Format(fconc * fvol / sconc, "#,##0.00") & " ul

End Su

Thanks in advanc