Can I apply more than one function to the same cell?

Dear STL Team,

Scenario: Staff have bough a new phone but if the phone is less than £250 they do not pay for it. If it is over £250 they pay the difference.

I have used an IF function which works as follows. "Price">=250, "Price"-250, "No Charge". This returns no charge for all prices below £250 and gives me the difference for all the others. However, there is a twist. Some cells in the price column do not contain a number so return an error message. I can delete the message leaving the cell blank. My question is how then can i create a formula to insert text into the blank cells which does not affect the IF function?

Many thanks

Matthew