If you know how to define a named ranged then try this:
Define a range
Name: IsFormula
Refers to: =LEFT(GET.CELL(6,INDIRECT("rc",FALSE)),1)="="
Then get out of this dialog box.
Next, select the all of the sells that you would like to conditionally format (that is, select all of the cells that you would like to test for a formula).
Go to the conditional format dialog box and type this condition:
Formula Is: =IsFormula