showing difference value with out going over ref cell

Example: a-c=d not to exceed value of b meaning b is the max value but need true number if it is below b

this is what I am doing tomake more sense of my question... this is regarding an insurance claim....col. a is total cost with tax, column b is depreciation value, col c is (a minus b), total with tax less depreciation which is acv......if they buy an item to replace it (Entered in column d) and it costs more than a ... the max they can have is b( dep value) but if it is less it should equal replacement cost (D)minus amount of total with tax (a) ..... you cant make money off insurance claim so if it cost more they max out at the difference being total depreciation is recoverable..

This is what I would do...

cost depcr diff replacement status
$40.00 $30.00 $10.00 $8.00 approved
$35.00 $30.00 $5.00 $5.00 approved
$40.00 $30.00 $10.00 $12.00 over limit
$5.00 $3.00 $2.00 $3.00 over limit
$15.00 $1.00 $14.00 $12.00 approved

Col E has the following formula
=IF(D1>C1,"over limit","approved")