show a blank cell if no data in a certain range

I have a simple formula where the data in 2cells (C3+D3) is added, then multiplied by 30.

However I want that cell to be blank if neither C3 nor D3 has data in them.
The syntax on my IF formula is obviously wrong but I don't know how to fix it.
This is my humble effort:


=IF(C3:D3"","",((C3+D3)*30))
Thankyou to anyone who can help
Maztaz

Yes, it works a treat.
Thankyou for your help.
Maztaz