Dynamic Control Reference?

is it possible to refer to a control dynamically?

i need to refer to one textbox if the value in a related and similarly named textbox meets a certain condition.

for example:

txt_MMC_Fail_Rate and txt_MMC_Fail_Count

if the (calculated) value in txt_MMC_Fail_Rate exceeds 3%, i need the backcolor of each of these controls to change to hilight the failure to the user.

i'm iterating through the controls collection, but can't figure out how to refer to the fail rate when i'm looking at txt_MMC_Fail_Count. what i hope to be able to do is strip off "Count" from the current control's name and append "Rate", then use that value to refer to the txt_MMC_Fail_Rate control.

is this possible? if so, could someone educate me, because all my attempts have failed...

thanks,
john

(edit: i am aware of the conditional formatting available directly on the control, but prefer not to go that route if possible. due to the number of controls involved, and the fact that documenter does not pick up conditional formats, i prefer to do this in code.)