Looks Greek To Me...

I have searched the forums for an answer, either there is not one or I missed keyword somehow.

I have a form (frmA) with a combo box to choose company (cboCompanyName). In this form there is a subform (frmA subform) ->Everything works great...

Within the subform I have another combobox (cboCommissionRate) and a check box (bxNonMPCI).

When the user ticks the checkbox I would like to:
If cboCompanyName = Company 1 then cboCommissionRate * .5
If cbocompanyName = Company 2 then cboCommissionRate - 1% (This one I figured out by placing a unbound text box with default value of 1%. And using if/then)

Now, if the check box is ticked by mistake, then cboCommissionRate reverts back to previous chosen amount.

I think this is nested iif or if or just plain if:) Maybe a dim I dunno

I am seeking assistance and appreciate any that is given

Thank you