Dragging a formula right while skipping two columns

[APNADTITON]

I have a formula typed into cell C1 currently. I need this formula to be repeated in F1, I1, L1 etc. How can I drag this formula across all the way until cell BZ1?

Essentially, I am skipping two columns each time.

 

[oldbrewer]

could you only invoke the formula if the 2 cells to the left (A1 and B1 ) are blank?

 

[APNADTITON]

A1 and B1 both have data in them.

 

[RoryA]

Do you have data in D1:E1, G1:H1 etc? If not, just select C1:E1 and then drag the fill handle across.

 

[APNADTITON]

Yes. There is data in every cell. I just don't want the formula to apply to the two in between. I need the formula to apply to every third column.

 

[RoryA]

Then you will have to copy and paste it - either manually or in code.