shortest distance between a point and a line

Hi,

I'm trying to formulate the shortest distance between a line and a point.

Please see attahced picture for the formula.

To translate it into Excel I'm having great difficulties and only getting #REF! as an outcome. Here's my attempt.

=SQRT((((TinyTri!I4+(Paras!A1*TinyTri!J4)-(Paras!A1*Paras!C1))/((Paras!A1)^2+1))-TinyTri!I4)^2)+((Paras!A1((TinyTri!I4+(Paras!A1*TinyTri!J4)-(Paras!A1*Paras!C1))/(Paras!A1^2+1))+Paras!C1-TinyTri!J4)^2)

TinyTri!I4 = Px
TinyTri!J4 = Py
Paras!A1 = m
Paras!C1 = c


Does anyone have an eagle eye for bracket placement?