Recalculate selcted rows based on a condition

Hi,

I want to be able to control which calculations within a sheet that are being preformed based upon the necessity of recalculation set by a true/false condition in the form IF(>0;true;false).

The sheet contains 8000 rows preforming the same calculation, but with 8000 different input conditions. However, based on separate input I only require somewhere between 500-1500 of these 8000 calculations to be updated. The idea is that this will save some time on the calulations, hence speeding up the program.

Is it possible to write a macro in VBA that does this?

Psuedo-code:

IF Value in Column M, Row (j) >0
Then recalculate Row(j)
Else Do Nothing

Secondly, will this actually save me some time on the total simulation?
Note: In each row there are 53 colums of data being updated, some with IF, MAX, VBA UDFs etc. In addition to a loop which affects about 10 of columns.

I hope my question was understandable and that someone can assist me. If additional specification is neccessary please let me know.

In contextual vba help we can find this:

"Worksheet.Calculate Method
To calculate:
1. All open workbooks => Application.Calculate (or just Calculate)
2. A specific worksheet => Worksheets(1).Calculate
3. A specified range => Worksheets(1).Rows(2).Calculate

Example: This example calculates the formulas in columns A, B, and C in the used range on Sheet1."

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Try to put it into practice.

I attempted to write a sub based upon your answer, however the intended functionality is not observed. Why this is so im not sure, but what i want from it is as mentioned to only update the values in the rows that meet the condition.

Sub Calculate_Range()
Dim i As Long
For i = 4 To 8004

If Sheets("Sheet1").Range(i, 13).Value > 0 Then

Sheets("Sheet2").Rows(i).Calculate

Next i
End Sub