I am trying to replacate this IF statement in reporting: =IF(I21>0,I21*1.3 E21,I21 E21)

I am trying to replicate this IF statement from excel to narrative reporting:

=IF(G21>0,G21*1.3+C21,G21+C21)

Of course the "21" refers to a cell in excel, however, I'd like to refer to a column.

When I try IFTHEN([G]>0 ,([G]) * 1.3 + ([C]),[G],[C]), I get an error saying I have a syntax error at or after "(" at the character position 15. What am I doing wrong?