Using a cell ref. with AVERAGEIF & INDIRECT in this example.

Please help to fix my Excel expression. The following works and returns the average value in the range, as long as values are <0.35. 

=AVERAGEIF(INDIRECT(($AE$5&":"&$AG$5)),"<0.35")

When I replace <0.35 with a cell reference, the expression no longer works, eg:-

=AVERAGEIF(INDIRECT(($AE$5&":"&$AG$5)),"<'Calcs!R2'")

Is there a correct way to replace the value 0.35 with its cell reference?

Thank you!