R code for creating "if... then" statement for a range of values of two variables

I am trying to create an "if... then" statement in R in which two variables, G1 and G2, lie within a range of values in a given dataset. For example, if (200 > G1 > -100) and (200 > G2 > -100), then G = mean(G1,G2)

My code looks like this:

if(200 > G1 > -100 & 200 > G2 > -100) {G = mean(G1,G2)}

The error I'm getting reads: Error: unexpected '>' in " if(200 > G1 >"

Any help would be much appreciated! Thanks