Changing the value in one cell to make two other cells equal (Goal Seek?)

Hello all, hoping for some help on this problem. Apologies if the title is not very descriptive, but I'm not sure how to describe this....

I have a spreadsheet that calculates stock trading signals using the daily stock price data as the input data.

I column C is the daily "high" price. Increasing the value in one row of column C causes (via a series of intermediate calculations) the figure in column M in the same row to increase, and the figure in column N to decrease. Initially, the value in N is higher than M, but I need to calculate the reversal point. At a certain value in column C, the values in column M and N will be equal - this is effectively the "crossover" point, where M becomes higher than N.

I can of course find this value of C by plugging in numbers using trial and error, but I need to do this multiple times and so want to automate it.

Can this be done automatically in Excel? I can't use Goal Seek since there is no fixed value for M or N, the "goal" is to make M and N equal.

Any help would be greatly appreciated! I don't really want to post the spreadsheet as it's huge and somewhat confusing!

Thanks!

I've attached a stripped-down version of the spreadsheet here, taking out most of the data to keep it manageable...

In row 119 I've highlighted the relevant cells (I got my columns wrong in the original post, it's actually C, L and M.)

In the previous row (118), column M is higher than column L. Increasing the value in C119 will cause L119 to increase and M119 to decrease, until L119 and M119 cross-over. The value in C119 in the spreadsheet is higher than it needs to be to get L119 and M119 to crossover. What I'd like to do is have some way of finding out what value in C119 will cause M119 to equal L119. (from trial and error, it's 1718.55, but I would like to have excel calculate this for me).

Hope this makes sense!

Well thanks anyway for trying. It's got me perplexed for sure... I'm wondering if I could use some sort of interpolation technique to get an approximate answer (which would be better than nothing), but can't figure it out....