I'm trying to set up a function in "data validation", "other".

=IF(OR(H1="Agency",H1="Employee Traveler")," ",0.5)

So far this works. However, I want to modify it to allow the user to input
any amount if it returns false. Is there a way to do this within the
function above or do I need to delve more into VBA?

Any amount of help would be grand.